python
diff --git a/‎Doc/library/idle.rst‎
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diff --git a/‎Doc/whatsnew/3.7.rst‎
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diff --git a/‎Lib/idlelib/codecontext.py‎
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diff --git a/‎Lib/idlelib/config-highlight.def‎
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diff --git a/‎Lib/idlelib/config-main.def‎
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diff --git a/‎Lib/idlelib/config.py‎
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diff --git a/‎Lib/idlelib/configdialog.py‎
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@@ -290,22 +290,31 @@ Options menu (Shell and Editor)
 Configure IDLE
    Open a configuration dialog and change preferences for the following:
    fonts, indentation, keybindings, text color themes, startup windows and
-   size, additional help sources, and extensions.  On macOS,  open the
+   size, additional help sources, and extensions.  On macOS, open the
    configuration dialog by selecting Preferences in the application
-   menu. For more, see
+   menu. For more details, see
    :ref:`Setting preferences <preferences>` under Help and preferences.
 
+   Most configuration options apply to all windows or all future windows.
+   The option items below only apply to the active window.
+
 Show/Hide Code Context (Editor Window only)
    Open a pane at the top of the edit window which shows the block context
    of the code which has scrolled above the top of the window.  See
-   :ref:`Code Context <code-context>` in the Editing and Navigation section below.
+   :ref:`Code Context <code-context>` in the Editing and Navigation section
+   below.
+
+Show/Hide Line Numbers (Editor Window only)
+   Open a column to the left of the edit window which shows the number
+   of each line of text.  The default is off, which may be changed in the
+   preferences (see :ref:`Setting preferences <preferences>`).
 
 Zoom/Restore Height
    Toggles the window between normal size and maximum height. The initial size
    defaults to 40 lines by 80 chars unless changed on the General tab of the
    Configure IDLE dialog.  The maximum height for a screen is determined by
    momentarily maximizing a window the first time one is zoomed on the screen.
-   Changing screen settings may invalidate the saved height.  This toogle has
+   Changing screen settings may invalidate the saved height.  This toggle has
    no effect when a window is maximized.
 
 Window menu (Shell and Editor)
 
@@ -1017,6 +1017,13 @@ by right-clicking the button.  (Contributed by Tal Einat in :issue:`1529353`.)
 
 The changes above have been backported to 3.6 maintenance releases.
 
+New in 3.7.5:
+
+Add optional line numbers for IDLE editor windows. Windows
+open without line numbers unless set otherwise in the General
+tab of the configuration dialog.
+(Contributed by Tal Einat and Saimadhav Heblikar in :issue:`17535`.)
+
 
 importlib
 ---------
 
@@ -13,7 +13,7 @@
 from sys import maxsize as INFINITY
 
 import tkinter
-from tkinter.constants import TOP, X, SUNKEN
+from tkinter.constants import NSEW, SUNKEN
 
 from idlelib.config import idleConf
 
@@ -67,6 +67,7 @@ def __init__(self, editwin):
 
     def _reset(self):
         self.context = None
+        self.cell00 = None
         self.t1 = None
         self.topvisible = 1
         self.info = [(0, -1, "", False)]
@@ -105,25 +106,37 @@ def toggle_code_context_event(self, event=None):
             padx = 0
             border = 0
             for widget in widgets:
-                padx += widget.tk.getint(widget.pack_info()['padx'])
+                info = (widget.grid_info()
+                        if widget is self.editwin.text
+                        else widget.pack_info())
+                padx += widget.tk.getint(info['padx'])
                 padx += widget.tk.getint(widget.cget('padx'))
                 border += widget.tk.getint(widget.cget('border'))
             self.context = tkinter.Text(
-                self.editwin.top, font=self.text['font'],
+                self.editwin.text_frame,
                 height=1,
                 width=1,  # Don't request more than we get.
+                highlightthickness=0,
                 padx=padx, border=border, relief=SUNKEN, state='disabled')
+            self.update_font()
             self.update_highlight_colors()
             self.context.bind('<ButtonRelease-1>', self.jumptoline)
             # Get the current context and initiate the recurring update event.
             self.timer_event()
-            # Pack the context widget before and above the text_frame widget,
-            # thus ensuring that it will appear directly above text_frame.
-            self.context.pack(side=TOP, fill=X, expand=False,
-                              before=self.editwin.text_frame)
+            # Grid the context widget above the text widget.
+            self.context.grid(row=0, column=1, sticky=NSEW)
+
+            line_number_colors = idleConf.GetHighlight(idleConf.CurrentTheme(),
+                                                       'linenumber')
+            self.cell00 = tkinter.Frame(self.editwin.text_frame,
+                                        bg=line_number_colors['background'])
+            self.cell00.grid(row=0, column=0, sticky=NSEW)
             menu_status = 'Hide'
         else:
             self.context.destroy()
+            self.context = None
+            self.cell00.destroy()
+            self.cell00 = None
             self.text.after_cancel(self.t1)
             self._reset()
             menu_status = 'Show'
@@ -221,8 +234,9 @@ def timer_event(self):
             self.update_code_context()
             self.t1 = self.text.after(self.UPDATEINTERVAL, self.timer_event)
 
-    def update_font(self, font):
+    def update_font(self):
         if self.context is not None:
+            font = idleConf.GetFont(self.text, 'main', 'EditorWindow')
             self.context['font'] = font
 
     def update_highlight_colors(self):
@@ -231,6 +245,11 @@ def update_highlight_colors(self):
             self.context['background'] = colors['background']
             self.context['foreground'] = colors['foreground']
 
+        if self.cell00 is not None:
+            line_number_colors = idleConf.GetHighlight(idleConf.CurrentTheme(),
+                                                       'linenumber')
+            self.cell00.config(bg=line_number_colors['background'])
+
 
 CodeContext.reload()
 
 
@@ -22,6 +22,10 @@ hit-foreground= #ffffff
 hit-background= #000000
 error-foreground= #000000
 error-background= #ff7777
+context-foreground= #000000
+context-background= lightgray
+linenumber-foreground= gray
+linenumber-background= #ffffff
 #cursor (only foreground can be set, restart IDLE)
 cursor-foreground= black
 #shell window
@@ -31,8 +35,6 @@ stderr-foreground= red
 stderr-background= #ffffff
 console-foreground= #770000
 console-background= #ffffff
-context-foreground= #000000
-context-background= lightgray
 
 [IDLE New]
 normal-foreground= #000000
@@ -55,6 +57,10 @@ hit-foreground= #ffffff
 hit-background= #000000
 error-foreground= #000000
 error-background= #ff7777
+context-foreground= #000000
+context-background= lightgray
+linenumber-foreground= gray
+linenumber-background= #ffffff
 #cursor (only foreground can be set, restart IDLE)
 cursor-foreground= black
 #shell window
@@ -64,8 +70,6 @@ stderr-foreground= red
 stderr-background= #ffffff
 console-foreground= #770000
 console-background= #ffffff
-context-foreground= #000000
-context-background= lightgray
 
 [IDLE Dark]
 comment-foreground = #dd0000
@@ -97,3 +101,5 @@ comment-background = #002240
 break-foreground = #FFFFFF
 context-foreground= #ffffff
 context-background= #454545
+linenumber-foreground= gray
+linenumber-background= #002240
@@ -36,7 +36,7 @@
 # Additional help sources are listed in the [HelpFiles] section below
 # and should be viewable by a web browser (or the Windows Help viewer in
 # the case of .chm files). These sources will be listed on the Help
-# menu.  The pattern, and two examples, are
+# menu.  The pattern, and two examples, are:
 #
 # <sequence_number = menu item;/path/to/help/source>
 # 1 = IDLE;C:/Programs/Python36/Lib/idlelib/help.html
@@ -46,7 +46,7 @@
 # platform specific because of path separators, drive specs etc.
 #
 # The default files should not be edited except to add new sections to
-# config-extensions.def for added extensions .  The user files should be
+# config-extensions.def for added extensions.  The user files should be
 # modified through the Settings dialog.
 
 [General]
@@ -65,6 +65,7 @@ font= TkFixedFont
 font-size= 10
 font-bold= 0
 encoding= none
+line-numbers-default= 0
 
 [PyShell]
 auto-squeeze-min-lines= 50
 
@@ -319,6 +319,10 @@ def GetThemeDict(self, type, themeName):
                 'hit-background':'#000000',
                 'error-foreground':'#ffffff',
                 'error-background':'#000000',
+                'context-foreground':'#000000',
+                'context-background':'#ffffff',
+                'linenumber-foreground':'#000000',
+                'linenumber-background':'#ffffff',
                 #cursor (only foreground can be set)
                 'cursor-foreground':'#000000',
                 #shell window
@@ -328,11 +332,11 @@ def GetThemeDict(self, type, themeName):
                 'stderr-background':'#ffffff',
                 'console-foreground':'#000000',
                 'console-background':'#ffffff',
-                'context-foreground':'#000000',
-                'context-background':'#ffffff',
                 }
         for element in theme:
-            if not cfgParser.has_option(themeName, element):
+            if not (cfgParser.has_option(themeName, element) or
+                    # Skip warning for new elements.
+                    element.startswith(('context-', 'linenumber-'))):
                 # Print warning that will return a default color
                 warning = ('\n Warning: config.IdleConf.GetThemeDict'
                            ' -\n problem retrieving theme element %r'
 
@@ -819,6 +819,7 @@ def create_page_highlight(self):
             'Shell Error Text': ('error', '12'),
             'Shell Stdout Text': ('stdout', '13'),
             'Shell Stderr Text': ('stderr', '14'),
+            'Line Number': ('linenumber', '16'),
             }
         self.builtin_name = tracers.add(
                 StringVar(self), self.var_changed_builtin_name)
@@ -866,6 +867,11 @@ def create_page_highlight(self):
             ('stderr', 'stderr'), ('\n\n', 'normal'))
         for texttag in text_and_tags:
             text.insert(END, texttag[0], texttag[1])
+        n_lines = len(text.get('1.0', END).splitlines())
+        for lineno in range(1, n_lines + 1):
+            text.insert(f'{lineno}.0',
+                        f'{lineno:{len(str(n_lines))}d} ',
+                        'linenumber')
         for element in self.theme_elements:
             def tem(event, elem=element):
                 # event.widget.winfo_top_level().highlight_target.set(elem)
@@ -1827,6 +1833,9 @@ def create_page_general(self):
                 frame_format: Frame
                     format_width_title: Label
                     (*)format_width_int: Entry - format_width
+                frame_line_numbers_default: Frame
+                    line_numbers_default_title: Label
+                    (*)line_numbers_default_bool: Checkbutton - line_numbers_default
                 frame_context: Frame
                     context_title: Label
                     (*)context_int: Entry - context_lines
@@ -1866,6 +1875,9 @@ def create_page_general(self):
                 IntVar(self), ('main', 'General', 'autosave'))
         self.format_width = tracers.add(
                 StringVar(self), ('extensions', 'FormatParagraph', 'max-width'))
+        self.line_numbers_default = tracers.add(
+                BooleanVar(self),
+                ('main', 'EditorWindow', 'line-numbers-default'))
         self.context_lines = tracers.add(
                 StringVar(self), ('extensions', 'CodeContext', 'maxlines'))
 
@@ -1944,6 +1956,14 @@ def create_page_general(self):
                 validatecommand=self.digits_only, validate='key',
         )
 
+        frame_line_numbers_default = Frame(frame_editor, borderwidth=0)
+        line_numbers_default_title = Label(
+            frame_line_numbers_default, text='Show line numbers in new windows')
+        self.line_numbers_default_bool = Checkbutton(
+                frame_line_numbers_default,
+                variable=self.line_numbers_default,
+                width=1)
+
         frame_context = Frame(frame_editor, borderwidth=0)
         context_title = Label(frame_context, text='Max Context Lines :')
         self.context_int = Entry(
@@ -2021,6 +2041,10 @@ def create_page_general(self):
         frame_format.pack(side=TOP, padx=5, pady=0, fill=X)
         format_width_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
         self.format_width_int.pack(side=TOP, padx=10, pady=5)
+        # frame_line_numbers_default.
+        frame_line_numbers_default.pack(side=TOP, padx=5, pady=0, fill=X)
+        line_numbers_default_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
+        self.line_numbers_default_bool.pack(side=LEFT, padx=5, pady=5)
         # frame_context.
         frame_context.pack(side=TOP, padx=5, pady=0, fill=X)
         context_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
@@ -2063,6 +2087,8 @@ def load_general_cfg(self):
                 'main', 'General', 'autosave', default=0, type='bool'))
         self.format_width.set(idleConf.GetOption(
                 'extensions', 'FormatParagraph', 'max-width', type='int'))
+        self.line_numbers_default.set(idleConf.GetOption(
+                'main', 'EditorWindow', 'line-numbers-default', type='bool'))
         self.context_lines.set(idleConf.GetOption(
                 'extensions', 'CodeContext', 'maxlines', type='int'))