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</style></head><body style="overflow: auto;"><div tabindex="2" class="cell text_cell border-box-sizing ui-widget-content ui-corner-all"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Hello, world!</h1></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [2]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print "Hello, world!"</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"Hello, world!"</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>Hello, world!</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [3]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print "Hello, world!"</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">sayhello</span><span class="cm-null">():</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"Hello, world!"</span></pre></div></div></div></div></div></div></div></div></div><div style="display: none;" class="output vbox"></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [4]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>sayhello()</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">sayhello</span><span class="cm-null">()</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>Hello, world!</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [5]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print "Hello, " + name</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">sayhello</span><span class="cm-null">(</span><span class="cm-variable">name</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"Hello, "</span><span class="cm-null"> </span><span class="cm-operator">+</span><span class="cm-null"> </span><span class="cm-variable">name</span></pre></div></div></div></div></div></div></div></div></div><div style="display: none;" class="output vbox"></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [6]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>sayhello('Rick')</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">sayhello</span><span class="cm-null">(</span><span class="cm-string">'Rick'</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>Hello, Rick</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 2px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p><strong>Exercise</strong>: Write a “Hello, world” program that uses
a function with a parameter to greet you by name</p></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Basic types</h1></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [7]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>1 # integer</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">1</span><span class="cm-null"> </span><span class="cm-comment"># integer</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[7]:</div><div class="box_flex1 output_subarea output_text"><pre>1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [8]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>3.14 # floating-point</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">3.14</span><span class="cm-null"> </span><span class="cm-comment"># floating-point</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[8]:</div><div class="box_flex1 output_subarea output_text"><pre>3.14</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [9]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>3.14e17 # floating-point (scientific notation)</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">3.14e17</span><span class="cm-null"> </span><span class="cm-comment"># floating-point (scientific notation)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[9]:</div><div class="box_flex1 output_subarea output_text"><pre>3.14e+17</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [10]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>123456789123456789123456789 # long integer (unbounded)</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">123456789123456789123456789</span><span class="cm-null"> </span><span class="cm-comment"># long integer (unbounded)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[10]:</div><div class="box_flex1 output_subarea output_text"><pre>123456789123456789123456789L</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [11]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># Type introspection</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># Type introspection</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-builtin">type</span><span class="cm-null">(</span><span class="cm-number">4</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-builtin">type</span><span class="cm-null">(</span><span class="cm-number">3.14</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre><type 'int'>
<type 'float'></pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [12]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>1 + 1j</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">1</span><span class="cm-null"> </span><span class="cm-operator">+</span><span class="cm-null"> </span><span class="cm-number">1j</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[12]:</div><div class="box_flex1 output_subarea output_text"><pre>(1+1j)</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [13]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>1j * 1j</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">1j</span><span class="cm-null"> </span><span class="cm-operator">*</span><span class="cm-null"> </span><span class="cm-number">1j</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[13]:</div><div class="box_flex1 output_subarea output_text"><pre>(-1+0j)</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Variables and basic arithmetic</h1></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [14]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>x = 1</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-number">1</span></pre><pre><span class="cm-variable">x</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[14]:</div><div class="box_flex1 output_subarea output_text"><pre>1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [15]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>x + 1</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">+</span><span class="cm-null"> </span><span class="cm-number">1</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[15]:</div><div class="box_flex1 output_subarea output_text"><pre>2</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [16]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y = x * 5</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> = </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">*</span><span class="cm-null"> </span><span class="cm-number">5</span></pre><pre><span class="cm-variable">y</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[16]:</div><div class="box_flex1 output_subarea output_text"><pre>5</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [17]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y *= 3 # in-place assigment</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> *= </span><span class="cm-number">3</span><span class="cm-null"> </span><span class="cm-comment"># in-place assigment</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">y</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>15</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [18]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y % 2 # modulo arithmetic</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> </span><span class="cm-operator">%</span><span class="cm-null"> </span><span class="cm-number">2</span><span class="cm-null"> </span><span class="cm-comment"># modulo arithmetic</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[18]:</div><div class="box_flex1 output_subarea output_text"><pre>1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [19]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y / 2 # result dependent on Python version</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> </span><span class="cm-operator">/</span><span class="cm-null"> </span><span class="cm-number">2</span><span class="cm-null"> </span><span class="cm-comment"># result dependent on Python version</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[19]:</div><div class="box_flex1 output_subarea output_text"><pre>7</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [20]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y / 2.0 # force floating point</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> </span><span class="cm-operator">/</span><span class="cm-null"> </span><span class="cm-number">2.0</span><span class="cm-null"> </span><span class="cm-comment"># force floating point</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[20]:</div><div class="box_flex1 output_subarea output_text"><pre>7.5</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [21]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y // 2.0 # force integer (floor) division)</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> </span><span class="cm-operator">//</span><span class="cm-null"> </span><span class="cm-number">2.0</span><span class="cm-null"> </span><span class="cm-comment"># force integer (floor) division)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[21]:</div><div class="box_flex1 output_subarea output_text"><pre>7.0</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [22]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>2==2</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">2</span><span class="cm-operator">==</span><span class="cm-number">2</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[22]:</div><div class="box_flex1 output_subarea output_text"><pre>True</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [23]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>2 <= 1 # comparisons are < > <= >= == !=</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">2</span><span class="cm-null"> </span><span class="cm-operator"><=</span><span class="cm-null"> </span><span class="cm-number">1</span><span class="cm-null"> </span><span class="cm-comment"># comparisons are < > <= >= == !=</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[23]:</div><div class="box_flex1 output_subarea output_text"><pre>False</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [84]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>2 != 3</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-number">2</span><span class="cm-null"> </span><span class="cm-operator">!=</span><span class="cm-null"> </span><span class="cm-number">3</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[84]:</div><div class="box_flex1 output_subarea output_text"><pre>True</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [85]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># exponentiation</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># exponentiation</span></pre><pre><span class="cm-number">2</span><span class="cm-null"> </span><span class="cm-operator">**</span><span class="cm-null"> </span><span class="cm-number">4</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[85]:</div><div class="box_flex1 output_subarea output_text"><pre>16</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [25]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>True and False</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">True</span><span class="cm-null"> </span><span class="cm-operator">and</span><span class="cm-null"> </span><span class="cm-variable">False</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[25]:</div><div class="box_flex1 output_subarea output_text"><pre>False</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [26]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>True or False</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">True</span><span class="cm-null"> </span><span class="cm-operator">or</span><span class="cm-null"> </span><span class="cm-variable">False</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[26]:</div><div class="box_flex1 output_subarea output_text"><pre>True</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [27]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>True and not False</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">True</span><span class="cm-null"> </span><span class="cm-operator">and</span><span class="cm-null"> </span><span class="cm-operator">not</span><span class="cm-null"> </span><span class="cm-variable">False</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[27]:</div><div class="box_flex1 output_subarea output_text"><pre>True</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Strings</h1></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [28]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print 'This is a string with single quotes'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This is a string with single quotes'</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"This is a string with double quotes"</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>This is a string with single quotes
This is a string with double quotes</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [29]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print "But we must escape \"double quotes\" inside double quotes and single quotes inside single quotes"</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"We can embed 'single quotes' within double quotes without escaping"</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'We can also embed "double quotes" within single quotes without escaping'</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"But we must escape \"double quotes\" inside double quotes and single quotes inside single quotes"</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>We can embed 'single quotes' within double quotes without escaping
We can also embed "double quotes" within single quotes without escaping
But we must escape "double quotes" inside double quotes and single quotes inside single quotes</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [30]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print "Strings can be" + " concatenated together " + "using the '+' operator"</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">"Strings can be"</span><span class="cm-null"> </span><span class="cm-operator">+</span><span class="cm-null"> </span><span class="cm-string">" concatenated together "</span><span class="cm-null"> </span><span class="cm-operator">+</span><span class="cm-null"> </span><span class="cm-string">"using the '+' operator"</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>Strings can be concatenated together using the '+' operator</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [31]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print '''We can also begin a string with three single-quote characters </span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'''We can also begin a string with three single-quote characters </span></pre><pre><span class="cm-string">or three double-quote characters. This allows us to build multi-line</span></pre><pre><span class="cm-string">strings without using the \\n escape sequence.'''</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>We can also begin a string with three single-quote characters
or three double-quote characters. This allows us to build multi-line
strings without using the \n escape sequence.</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [32]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print u'You can use encoded unicode characters in your source code: 海淀区科学院南路2号融科资讯中心C座南楼8层'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">u'Unicode strings have a "u" prefix.'</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">u'You can use encoded unicode characters in your source code: 海淀区科学院南路2号融科资讯中心C座南楼8层'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>Unicode strings have a "u" prefix.
You can use encoded unicode characters in your source code: 海淀区科学院南路2号融科资讯中心C座南楼8层</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 9px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>We <em>can</em> use escape sequences inside strings, however. Escape sequences start with a backslash character (). Some common
escape sequences appear below:</p>
<ul>
<li>\n - newline</li>
<li>\r - carriage return</li>
<li>\t - tab character</li>
<li>\ - literal backslash</li>
<li>\x20 - hex escape (in this case, ASCII character 0x20, the space)</li>
<li>\u4e0b - unicode escape (hex sequence)</li>
</ul></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 3px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>You can index into a string using either a single integer or
a "slice." The result is always another string (there is no
'char' type in Python).</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [33]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s = 'The quick brown fox'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null"> = </span><span class="cm-string">'The quick brown fox'</span></pre><pre><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-number">0</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[33]:</div><div class="box_flex1 output_subarea output_text"><pre>'T'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [34]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>type(s[0])</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-builtin">type</span><span class="cm-null">(</span><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-number">0</span><span class="cm-null">])</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[34]:</div><div class="box_flex1 output_subarea output_text"><pre>str</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [35]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[1:15]</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-number">1</span><span class="cm-null">:</span><span class="cm-number">15</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[35]:</div><div class="box_flex1 output_subarea output_text"><pre>'he quick brown'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [36]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[1:15:2] # 'step' by 2</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-number">1</span><span class="cm-null">:</span><span class="cm-number">15</span><span class="cm-null">:</span><span class="cm-number">2</span><span class="cm-null">] </span><span class="cm-comment"># 'step' by 2</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[36]:</div><div class="box_flex1 output_subarea output_text"><pre>'h uc rw'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [37]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[:3] # beginning of range omitted</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[:</span><span class="cm-number">3</span><span class="cm-null">] </span><span class="cm-comment"># beginning of range omitted</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[37]:</div><div class="box_flex1 output_subarea output_text"><pre>'The'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [38]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[3:] # end of range omitted</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-number">3</span><span class="cm-null">:] </span><span class="cm-comment"># end of range omitted</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[38]:</div><div class="box_flex1 output_subarea output_text"><pre>' quick brown fox'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [39]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[-1] # negative indexing from the end </span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-operator">-</span><span class="cm-number">1</span><span class="cm-null">] </span><span class="cm-comment"># negative indexing from the end </span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[39]:</div><div class="box_flex1 output_subarea output_text"><pre>'x'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [40]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[-3:] # last 3 characters</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[</span><span class="cm-operator">-</span><span class="cm-number">3</span><span class="cm-null">:] </span><span class="cm-comment"># last 3 characters</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[40]:</div><div class="box_flex1 output_subarea output_text"><pre>'fox'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [41]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>s[::-1] # negative step reverses the sequence</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">s</span><span class="cm-null">[::</span><span class="cm-operator">-</span><span class="cm-number">1</span><span class="cm-null">] </span><span class="cm-comment"># negative step reverses the sequence</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[41]:</div><div class="box_flex1 output_subarea output_text"><pre>'xof nworb kciuq ehT'</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [86]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>len(s) # length of string</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">len</span><span class="cm-null">(</span><span class="cm-variable">s</span><span class="cm-null">) </span><span class="cm-comment"># length of string</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[86]:</div><div class="box_flex1 output_subarea output_text"><pre>19</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [89]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print len(x) # unicode length</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-string">u'海'</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">len</span><span class="cm-null">(</span><span class="cm-variable">x</span><span class="cm-null">) </span><span class="cm-comment"># unicode length</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [94]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>y = x.encode('utf-8') # encode to bytes ('str')</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">y</span><span class="cm-null"> = </span><span class="cm-variable">x.encode</span><span class="cm-null">(</span><span class="cm-string">'utf-8'</span><span class="cm-null">) </span><span class="cm-comment"># encode to bytes ('str')</span></pre><pre><span class="cm-variable">len</span><span class="cm-null">(</span><span class="cm-variable">y</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[94]:</div><div class="box_flex1 output_subarea output_text"><pre>3</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [96]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># decode utf-8 back to unicode</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># decode utf-8 back to unicode</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-builtin">unicode</span><span class="cm-null">(</span><span class="cm-variable">y</span><span class="cm-null">, </span><span class="cm-string">'utf-8'</span><span class="cm-null">) </span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>海</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 3px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Lists</h1>
<p>Lists are mutable, dynamically typed sequences, and they are used frequently in Python.</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [42]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># This is a list</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># This is a list</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> [ </span><span class="cm-number">1</span><span class="cm-null">,</span><span class="cm-number">2</span><span class="cm-null">,</span><span class="cm-number">3</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 2, 3]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [43]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 82px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># We can append to lists</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># We can append to lists</span></pre><pre><span class="cm-variable">lst</span><span class="cm-null"> = [ </span><span class="cm-number">1</span><span class="cm-null">, </span><span class="cm-number">2</span><span class="cm-null">, </span><span class="cm-number">3</span><span class="cm-null"> ]</span></pre><pre><span class="cm-variable">lst.append</span><span class="cm-null">(</span><span class="cm-number">4</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 2, 3, 4]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [44]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># We can index into lists (0-based indexing)</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># We can index into lists (0-based indexing)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span><span class="cm-null">[</span><span class="cm-number">2</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>3</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [45]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># We can insert, remove, and update</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># We can insert, remove, and update</span></pre><pre><span class="cm-variable">lst.insert</span><span class="cm-null">(</span><span class="cm-number">1</span><span class="cm-null">, </span><span class="cm-number">42</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 42, 2, 3, 4]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [46]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>lst.remove(2)</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">lst.remove</span><span class="cm-null">(</span><span class="cm-number">2</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 42, 3, 4]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [47]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>del lst[2]</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">del</span><span class="cm-null"> </span><span class="cm-variable">lst</span><span class="cm-null">[</span><span class="cm-number">2</span><span class="cm-null">]</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 42, 4]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [48]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>lst[1] = 43</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">lst</span><span class="cm-null">[</span><span class="cm-number">1</span><span class="cm-null">] = </span><span class="cm-number">43</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 43, 4]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [49]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># pop() removes and returns the last element</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># pop() removes and returns the last element</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst.pop</span><span class="cm-null">()</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>4</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [50]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print lst</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[1, 43]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [51]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>lst = [ 'This', 'is', 'a', 'list', 'with', 7, 'elements' ]</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># Lists are dynamically typed</span></pre><pre><span class="cm-variable">lst</span><span class="cm-null"> = [ </span><span class="cm-string">'This'</span><span class="cm-null">, </span><span class="cm-string">'is'</span><span class="cm-null">, </span><span class="cm-string">'a'</span><span class="cm-null">, </span><span class="cm-string">'list'</span><span class="cm-null">, </span><span class="cm-string">'with'</span><span class="cm-null">, </span><span class="cm-number">7</span><span class="cm-null">, </span><span class="cm-string">'elements'</span><span class="cm-null"> ]</span></pre><pre><span class="cm-variable">lst</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[51]:</div><div class="box_flex1 output_subarea output_text"><pre>['This', 'is', 'a', 'list', 'with', 7, 'elements']</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [52]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># Lists can be sliced just like strings</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># Lists can be sliced just like strings</span></pre><pre><span class="cm-variable">lst</span><span class="cm-null">[::</span><span class="cm-operator">-</span><span class="cm-number">2</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[52]:</div><div class="box_flex1 output_subarea output_text"><pre>['elements', 'with', 'a', 'This']</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 3px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Tuples</h1>
<p>Tuples are <em>immutable</em> sequences.</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [53]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># this is a tuple</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># this is a tuple</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> (</span><span class="cm-number">1</span><span class="cm-null">, </span><span class="cm-number">2</span><span class="cm-null">, </span><span class="cm-number">3</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>(1, 2, 3)</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [54]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print ('Tuples', 'are', 'also', 'dynamically', 'typed', 42)</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> (</span><span class="cm-string">'Tuples'</span><span class="cm-null">, </span><span class="cm-string">'are'</span><span class="cm-null">, </span><span class="cm-string">'also'</span><span class="cm-null">, </span><span class="cm-string">'dynamically'</span><span class="cm-null">, </span><span class="cm-string">'typed'</span><span class="cm-null">, </span><span class="cm-number">42</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>('Tuples', 'are', 'also', 'dynamically', 'typed', 42)</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [55]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># Tuples can be indexed</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># Tuples can be indexed</span></pre><pre><span class="cm-variable">t</span><span class="cm-null"> = (</span><span class="cm-number">1</span><span class="cm-null">,</span><span class="cm-number">2</span><span class="cm-null">,</span><span class="cm-number">3</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">t</span><span class="cm-null">[</span><span class="cm-number">0</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [56]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 82px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># Tuples can be "unpacked"</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># Tuples can be "unpacked"</span></pre><pre><span class="cm-variable">x</span><span class="cm-null">,</span><span class="cm-variable">y</span><span class="cm-null"> = (</span><span class="cm-number">1</span><span class="cm-null">,</span><span class="cm-number">2</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">x</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">y</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>1
2</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Basic control structures</h1></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [57]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 82px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print 'This is false'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">if</span><span class="cm-null"> </span><span class="cm-variable">True</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This is true'</span></pre><pre><span class="cm-keyword">else</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This is false'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>This is true</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [58]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 82px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> x = x + 1</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-number">0</span></pre><pre><span class="cm-keyword">while</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator"><</span><span class="cm-null"> </span><span class="cm-number">5</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">+</span><span class="cm-null"> </span><span class="cm-number">1</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">x</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>1
2
3
4
5</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [59]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>lst = [ 1, 2, 3 ]</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">lst</span><span class="cm-null"> = [ </span><span class="cm-number">1</span><span class="cm-null">, </span><span class="cm-number">2</span><span class="cm-null">, </span><span class="cm-number">3</span><span class="cm-null"> ]</span></pre><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-variable">lst</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">x</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>1
2
3</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [60]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>for x in range(3):</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">range</span><span class="cm-null">(</span><span class="cm-number">3</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-variable">range</span><span class="cm-null">(</span><span class="cm-number">3</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">x</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[0, 1, 2]
0
1
2</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [61]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>for x in xrange(3):</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-builtin">xrange</span><span class="cm-null">(</span><span class="cm-number">3</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-builtin">xrange</span><span class="cm-null">(</span><span class="cm-number">3</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">x</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>xrange(3)
0
1
2</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [62]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 100px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>for x in xrange(10):</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-builtin">xrange</span><span class="cm-null">(</span><span class="cm-number">10</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">if</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">%</span><span class="cm-null"> </span><span class="cm-number">2</span><span class="cm-null"> </span><span class="cm-operator">==</span><span class="cm-null"> </span><span class="cm-number">0</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">continue</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">if</span><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> </span><span class="cm-operator">></span><span class="cm-null"> </span><span class="cm-number">5</span><span class="cm-null">: </span><span class="cm-keyword">break</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">x</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>1
3
5</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 5px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h3>Exercises</h3>
<ul>
<li>Write a function that sums the values in a list using a <code>for</code> loop</li>
<li>Write a function that sums the even-numbered values in a list</li>
<li>Write a function that returns the reversed version of a list</li>
</ul></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 3px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Dicts</h1>
<p>A <em>dict</em> is a hash table (also known as a "dictionary"). Dicts are pervasive in Python.</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [63]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print { 'key': 'value' }</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> { </span><span class="cm-string">'key'</span><span class="cm-null">: </span><span class="cm-string">'value'</span><span class="cm-null"> }</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>{'key': 'value'}</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [64]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>d = { 'key1': 1, 'key2': 'foo' }</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">d</span><span class="cm-null"> = { </span><span class="cm-string">'key1'</span><span class="cm-null">: </span><span class="cm-number">1</span><span class="cm-null">, </span><span class="cm-string">'key2'</span><span class="cm-null">: </span><span class="cm-string">'foo'</span><span class="cm-null"> }</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>{'key2': 'foo', 'key1': 1}</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [65]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>d['key1']</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'key1'</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[65]:</div><div class="box_flex1 output_subarea output_text"><pre>1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [66]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>d['key3'] = 'bar'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'key3'</span><span class="cm-null">] = </span><span class="cm-string">'bar'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: none;" class="output vbox"></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [67]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print d</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>{'key3': 'bar', 'key2': 'foo', 'key1': 1}</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [68]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># dicts are unordered, but we can get a list of their keys,</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># dicts are unordered, but we can get a list of their keys,</span></pre><pre><span class="cm-comment"># values, or (key,value) pairs</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d.keys</span><span class="cm-null">()</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>['key3', 'key2', 'key1']</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [69]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print d.values()</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d.values</span><span class="cm-null">()</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>['bar', 'foo', 1]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [70]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print d.items()</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d.items</span><span class="cm-null">()</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>[('key3', 'bar'), ('key2', 'foo'), ('key1', 1)]</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [71]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span># dict keys can be any *immutable* type in Python</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># dict keys can be any *immutable* type in Python</span></pre><pre><span class="cm-variable">d</span><span class="cm-null"> = { </span><span class="cm-string">'foo'</span><span class="cm-null">: </span><span class="cm-number">1</span><span class="cm-null">, </span><span class="cm-number">2</span><span class="cm-null">: </span><span class="cm-string">'bar'</span><span class="cm-null"> }</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>{2: 'bar', 'foo': 1}</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [72]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>d[(1,2)] = 'baz'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">d</span><span class="cm-null">[(</span><span class="cm-number">1</span><span class="cm-null">,</span><span class="cm-number">2</span><span class="cm-null">)] = </span><span class="cm-string">'baz'</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>{(1, 2): 'baz', 2: 'bar', 'foo': 1}</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>Items can be removed using the <code>del</code> keyword</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [73]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>del d[2]</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">del</span><span class="cm-null"> </span><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-number">2</span><span class="cm-null">]</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">d</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>{(1, 2): 'baz', 'foo': 1}</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>A <code>dict</code> can be iterated through in a space-efficient using <code>iterkeys</code>, <code>itervalues</code>, and <code>iteritems</code>:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [74]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>for k in d.iterkeys():</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">k</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-variable">d.iterkeys</span><span class="cm-null">():</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">k</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>(1, 2)
foo</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [75]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>for v in d.itervalues():</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">v</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-variable">d.itervalues</span><span class="cm-null">():</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">v</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>baz
1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [76]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>for k,v in d.iteritems():</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">for</span><span class="cm-null"> </span><span class="cm-variable">k</span><span class="cm-null">,</span><span class="cm-variable">v</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-variable">d.iteritems</span><span class="cm-null">():</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">k</span><span class="cm-null">, </span><span class="cm-variable">v</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>(1, 2) baz
foo 1</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [77]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>'foo' in d # Test for key membership </span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-string">'foo'</span><span class="cm-null"> </span><span class="cm-operator">in</span><span class="cm-null"> </span><span class="cm-variable">d</span><span class="cm-null"> </span><span class="cm-comment"># Test for key membership </span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt output_prompt">Out[77]:</div><div class="box_flex1 output_subarea output_text"><pre>True</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 4px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Exceptions</h1>
<p>Python handles errors by throwing <em>exceptions</em>. For instance, trying to read a non-existent
key in a dict:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [78]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>d['does not exist']</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'does not exist'</span><span class="cm-null">]</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text"><pre><span class="ansired">---------------------------------------------------------------------------</span>
<span class="ansired">KeyError</span> Traceback (most recent call last)
<span class="ansigreen">/vagrant/<ipython-input-78-17d039c47522></span> in <span class="ansicyan"><module></span><span class="ansiblue">()</span>
<span class="ansigreen">----> 1</span><span class="ansired"> </span>d<span class="ansiblue">[</span><span class="ansiblue">'does not exist'</span><span class="ansiblue">]</span><span class="ansiblue"></span>
<span class="ansired">KeyError</span>: 'does not exist'
</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>To handle exceptions gracefully, we must enclose them in a <code>try:</code> <em>block</em>:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [79]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 100px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print 'This statement never executes!'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">try</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'does not exist'</span><span class="cm-null">]</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This statement never executes!'</span></pre><pre><span class="cm-keyword">except</span><span class="cm-null"> </span><span class="cm-variable">KeyError</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'There was a key error!'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>There was a key error!</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>We can also write code that will <em>always</em> run, whether an exception is raised or not:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [80]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 118px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print 'There was a key error!'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">try</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'does not exist'</span><span class="cm-null">]</span></pre><pre><span class="cm-keyword">except</span><span class="cm-null"> </span><span class="cm-variable">KeyError</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'There was a key error!'</span></pre><pre><span class="cm-keyword">finally</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This always runs!'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>There was a key error!
This always runs!</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [81]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 118px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print 'There was a key error!'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">try</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'key1'</span><span class="cm-null">]</span></pre><pre><span class="cm-keyword">except</span><span class="cm-null"> </span><span class="cm-variable">KeyError</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'There was a key error!'</span></pre><pre><span class="cm-keyword">finally</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This always runs!'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>There was a key error!
This always runs!</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>If we want code that only runs when there is <em>not</em> an error, we can use the <code>else:</code> clause:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [82]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 153px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print 'The try: block completed without error.'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">try</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">x</span><span class="cm-null"> = </span><span class="cm-variable">d</span><span class="cm-null">[</span><span class="cm-string">'key1'</span><span class="cm-null">]</span></pre><pre><span class="cm-keyword">except</span><span class="cm-null"> </span><span class="cm-variable">KeyError</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'There was a key error!'</span></pre><pre><span class="cm-keyword">else</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'The try: block completed without error.'</span></pre><pre><span class="cm-keyword">finally</span><span class="cm-null">:</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'This always runs!'</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>There was a key error!
This always runs!</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>To <em>cause</em> an exception, use the <code>raise</code> keyword:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [83]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>raise KeyError('This is a key error')</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">raise</span><span class="cm-null"> </span><span class="cm-variable">KeyError</span><span class="cm-null">(</span><span class="cm-string">'This is a key error'</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text"><pre><span class="ansired">---------------------------------------------------------------------------</span>
<span class="ansired">KeyError</span> Traceback (most recent call last)
<span class="ansigreen">/vagrant/<ipython-input-83-04dfd7050815></span> in <span class="ansicyan"><module></span><span class="ansiblue">()</span>
<span class="ansigreen">----> 1</span><span class="ansired"> </span><span class="ansigreen">raise</span> KeyError<span class="ansiblue">(</span><span class="ansiblue">'This is a key error'</span><span class="ansiblue">)</span><span class="ansiblue"></span>
<span class="ansired">KeyError</span>: 'This is a key error'
</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 8px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h3>Exercises</h3>
<ul>
<li>Write a collection of functions to manage a telephone directory. The directory should be
stored in a dict and passed as the first argument to each function. These functions should include
<code>add_number(directory, name, number)</code>, <code>remove_number(directory, name)</code>, and
<code>lookup_number(directory, name)</code>. </li>
<li>Update your function so that <code>remove_number</code> does not raise an exception when you remove a
non-existent entry.</li>
</ul></div></div><div style="height: 30%;" class="end_space"></div></body></html>
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