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thinkpython.py

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import contextlib

import io

import re

def extract_function_name(text):

"""Find a function definition and return its name.

text: String

returns: String or None

"""

pattern = r"def\s+(\w+)\s*\("

match = re.search(pattern, text)

if match:

func_name = match.group(1)

return func_name

else:

return None

# the functions that define cell magic commands are only defined

# if we're running in Jupyter.

try:

from IPython.core.magic import register_cell_magic

from IPython.core.magic_arguments import argument, magic_arguments, parse_argstring

@register_cell_magic

def add_method_to(args, cell):

# get the name of the function defined in this cell

func_name = extract_function_name(cell)

if func_name is None:

return f"This cell doesn't define any new functions."

# get the class we're adding it to

namespace = get_ipython().user_ns

class_name = args

cls = namespace.get(class_name, None)

if cls is None:

return f"Class '{class_name}' not found."

# save the old version of the function if it was already defined

old_func = namespace.get(func_name, None)

if old_func is not None:

del namespace[func_name]

# Execute the cell to define the function

get_ipython().run_cell(cell)

# get the newly defined function

new_func = namespace.get(func_name, None)

if new_func is None:

return f"This cell didn't define {func_name}."

# add the function to the class and remove it from the namespace

setattr(cls, func_name, new_func)

del namespace[func_name]

# restore the old function to the namespace

if old_func is not None:

namespace[func_name] = old_func

@register_cell_magic

def expect_error(line, cell):

try:

get_ipython().run_cell(cell)

except Exception as e:

get_ipython().run_cell("%tb")

@magic_arguments()

@argument("exception", help="Type of exception to catch")

@register_cell_magic

def expect(line, cell):

args = parse_argstring(expect, line)

exception = eval(args.exception)

try:

get_ipython().run_cell(cell)

except exception as e:

get_ipython().run_cell("%tb")

def traceback(mode):

"""Set the traceback mode.

mode: string

"""

with contextlib.redirect_stdout(io.StringIO()):

get_ipython().run_cell(f"%xmode {mode}")

traceback("Minimal")

except (ImportError, NameError):

print("Warning: IPython is not available, cell magic not defined.")