26.5. IDLE
**********

**Source code:** Lib/idlelib/

======================================================================

IDLE is Python’s Integrated Development and Learning Environment.

IDLE has the following features:

* coded in 100% pure Python, using the "tkinter" GUI toolkit

* cross-platform: works mostly the same on Windows, Unix, and Mac OS
  X

* Python shell window (interactive interpreter) with colorizing of
  code input, output, and error messages

* multi-window text editor with multiple undo, Python colorizing,
  smart indent, call tips, auto completion, and other features

* search within any window, replace within editor windows, and
  search through multiple files (grep)

* debugger with persistent breakpoints, stepping, and viewing of
  global and local namespaces

* configuration, browsers, and other dialogs


26.5.1. Menus
=============

IDLE has two main window types, the Shell window and the Editor
window.  It is possible to have multiple editor windows
simultaneously.  Output windows, such as used for Edit / Find in
Files, are a subtype of edit window.  They currently have the same top
menu as Editor windows but a different default title and context menu.

IDLE’s menus dynamically change based on which window is currently
selected. Each menu documented below indicates which window type it is
associated with.


26.5.1.1. File menu (Shell and Editor)
--------------------------------------

New File
   Create a new file editing window.

Open…
   Open an existing file with an Open dialog.

Recent Files
   Open a list of recent files.  Click one to open it.

Open Module…
   Open an existing module (searches sys.path).

Class Browser
   Show functions, classes, and methods in the current Editor file in
   a tree structure.  In the shell, open a module first.

Path Browser
   Show sys.path directories, modules, functions, classes and methods
   in a tree structure.

Save
   Save the current window to the associated file, if there is one.
   Windows that have been changed since being opened or last saved
   have a * before and after the window title.  If there is no
   associated file, do Save As instead.

Save As…
   Save the current window with a Save As dialog.  The file saved
   becomes the new associated file for the window.

Save Copy As…
   Save the current window to different file without changing the
   associated file.

Print Window
   Print the current window to the default printer.

Close
   Close the current window (ask to save if unsaved).

Exit
   Close all windows and quit IDLE (ask to save unsaved windows).


26.5.1.2. Edit menu (Shell and Editor)
--------------------------------------

Undo
   Undo the last change to the current window.  A maximum of 1000
   changes may be undone.

Redo
   Redo the last undone change to the current window.

Cut
   Copy selection into the system-wide clipboard; then delete the
   selection.

Copy
   Copy selection into the system-wide clipboard.

Paste
   Insert contents of the system-wide clipboard into the current
   window.

The clipboard functions are also available in context menus.

Select All
   Select the entire contents of the current window.

Find…
   Open a search dialog with many options

Find Again
   Repeat the last search, if there is one.

Find Selection
   Search for the currently selected string, if there is one.

Find in Files…
   Open a file search dialog.  Put results in a new output window.

Replace…
   Open a search-and-replace dialog.

Go to Line
   Move cursor to the line number requested and make that line
   visible.

Show Completions
   Open a scrollable list allowing selection of keywords and
   attributes. See Completions in the Tips sections below.

Expand Word
   Expand a prefix you have typed to match a full word in the same
   window; repeat to get a different expansion.

Show call tip
   After an unclosed parenthesis for a function, open a small window
   with function parameter hints.

Show surrounding parens
   Highlight the surrounding parenthesis.


26.5.1.3. Format menu (Editor window only)
------------------------------------------

Indent Region
   Shift selected lines right by the indent width (default 4 spaces).

Dedent Region
   Shift selected lines left by the indent width (default 4 spaces).

Comment Out Region
   Insert ## in front of selected lines.

Uncomment Region
   Remove leading # or ## from selected lines.

Tabify Region
   Turn *leading* stretches of spaces into tabs. (Note: We recommend
   using 4 space blocks to indent Python code.)

Untabify Region
   Turn *all* tabs into the correct number of spaces.

Toggle Tabs
   Open a dialog to switch between indenting with spaces and tabs.

New Indent Width
   Open a dialog to change indent width. The accepted default by the
   Python community is 4 spaces.

Format Paragraph
   Reformat the current blank-line-delimited paragraph in comment
   block or multiline string or selected line in a string.  All lines
   in the paragraph will be formatted to less than N columns, where N
   defaults to 72.

Strip trailing whitespace
   Remove trailing space and other whitespace characters after the
   last non-whitespace character of a line by applying str.rstrip to
   each line, including lines within multiline strings.


26.5.1.4. Run menu (Editor window only)
---------------------------------------

Python Shell
   Open or wake up the Python Shell window.

Check Module
   Check the syntax of the module currently open in the Editor window.
   If the module has not been saved IDLE will either prompt the user
   to save or autosave, as selected in the General tab of the Idle
   Settings dialog.  If there is a syntax error, the approximate
   location is indicated in the Editor window.

Run Module
   Do Check Module (above).  If no error, restart the shell to clean
   the environment, then execute the module.  Output is displayed in
   the Shell window.  Note that output requires use of "print" or
   "write". When execution is complete, the Shell retains focus and
   displays a prompt. At this point, one may interactively explore the
   result of execution. This is similar to executing a file with
   "python -i file" at a command line.


26.5.1.5. Shell menu (Shell window only)
----------------------------------------

View Last Restart
   Scroll the shell window to the last Shell restart.

Restart Shell
   Restart the shell to clean the environment.

Interrupt Execution
   Stop a running program.


26.5.1.6. Debug menu (Shell window only)
----------------------------------------

Go to File/Line
   Look on the current line. with the cursor, and the line above for a
   filename and line number.  If found, open the file if not already
   open, and show the line.  Use this to view source lines referenced
   in an exception traceback and lines found by Find in Files. Also
   available in the context menu of the Shell window and Output
   windows.

Debugger (toggle)
   When activated, code entered in the Shell or run from an Editor
   will run under the debugger.  In the Editor, breakpoints can be set
   with the context menu.  This feature is still incomplete and
   somewhat experimental.

Stack Viewer
   Show the stack traceback of the last exception in a tree widget,
   with access to locals and globals.

Auto-open Stack Viewer
   Toggle automatically opening the stack viewer on an unhandled
   exception.


26.5.1.7. 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
   (see below).  On OS X, open the configuration dialog by selecting
   Preferences in the application menu.  To use a new built-in color
   theme (IDLE Dark) with older IDLEs, save it as a new custom theme.

   Non-default user settings are saved in a .idlerc directory in the
   user’s home directory.  Problems caused by bad user configuration
   files are solved by editing or deleting one or more of the files in
   .idlerc.

Code Context (toggle)(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.
   Clicking a line in this pane exposes that line at the top of the
   editor.


26.5.1.8. Window menu (Shell and Editor)
----------------------------------------

Zoom 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 rest of this menu lists the names of all open windows; select one
to bring it to the foreground (deiconifying it if necessary).


26.5.1.9. Help menu (Shell and Editor)
--------------------------------------

About IDLE
   Display version, copyright, license, credits, and more.

IDLE Help
   Display a help file for IDLE detailing the menu options, basic
   editing and navigation, and other tips.

Python Docs
   Access local Python documentation, if installed, or start a web
   browser and open docs.python.org showing the latest Python
   documentation.

Turtle Demo
   Run the turtledemo module with example python code and turtle
   drawings.

Additional help sources may be added here with the Configure IDLE
dialog under the General tab.


26.5.1.10. Context Menus
------------------------

Open a context menu by right-clicking in a window (Control-click on OS
X). Context menus have the standard clipboard functions also on the
Edit menu.

Cut
   Copy selection into the system-wide clipboard; then delete the
   selection.

Copy
   Copy selection into the system-wide clipboard.

Paste
   Insert contents of the system-wide clipboard into the current
   window.

Editor windows also have breakpoint functions.  Lines with a
breakpoint set are specially marked.  Breakpoints only have an effect
when running under the debugger.  Breakpoints for a file are saved in
the user’s .idlerc directory.

Set Breakpoint
   Set a breakpoint on the current line.

Clear Breakpoint
   Clear the breakpoint on that line.

Shell and Output windows have the following.

Go to file/line
   Same as in Debug menu.


26.5.2. Editing and navigation
==============================

In this section, ‘C’ refers to the "Control" key on Windows and Unix
and the "Command" key on Mac OSX.

* "Backspace" deletes to the left; "Del" deletes to the right

* "C-Backspace" delete word left; "C-Del" delete word to the right

* Arrow keys and "Page Up"/"Page Down" to move around

* "C-LeftArrow" and "C-RightArrow" moves by words

* "Home"/"End" go to begin/end of line

* "C-Home"/"C-End" go to begin/end of file

* Some useful Emacs bindings are inherited from Tcl/Tk:

     * "C-a" beginning of line

     * "C-e" end of line

     * "C-k" kill line (but doesn’t put it in clipboard)

     * "C-l" center window around the insertion point

     * "C-b" go backward one character without deleting (usually you
       can also use the cursor key for this)

     * "C-f" go forward one character without deleting (usually you
       can also use the cursor key for this)

     * "C-p" go up one line (usually you can also use the cursor key
       for this)

     * "C-d" delete next character

Standard keybindings (like "C-c" to copy and "C-v" to paste) may work.
Keybindings are selected in the Configure IDLE dialog.


26.5.2.1. Automatic indentation
-------------------------------

After a block-opening statement, the next line is indented by 4 spaces
(in the Python Shell window by one tab).  After certain keywords
(break, return etc.) the next line is dedented.  In leading
indentation, "Backspace" deletes up to 4 spaces if they are there.
"Tab" inserts spaces (in the Python Shell window one tab), number
depends on Indent width. Currently, tabs are restricted to four spaces
due to Tcl/Tk limitations.

See also the indent/dedent region commands in the edit menu.


26.5.2.2. Completions
---------------------

Completions are supplied for functions, classes, and attributes of
classes, both built-in and user-defined. Completions are also provided
for filenames.

The AutoCompleteWindow (ACW) will open after a predefined delay
(default is two seconds) after a ‘.’ or (in a string) an os.sep is
typed. If after one of those characters (plus zero or more other
characters) a tab is typed the ACW will open immediately if a possible
continuation is found.

If there is only one possible completion for the characters entered, a
"Tab" will supply that completion without opening the ACW.

‘Show Completions’ will force open a completions window, by default
the "C-space" will open a completions window. In an empty string, this
will contain the files in the current directory. On a blank line, it
will contain the built-in and user-defined functions and classes in
the current namespaces, plus any modules imported. If some characters
have been entered, the ACW will attempt to be more specific.

If a string of characters is typed, the ACW selection will jump to the
entry most closely matching those characters.  Entering a "tab" will
cause the longest non-ambiguous match to be entered in the Editor
window or Shell.  Two "tab" in a row will supply the current ACW
selection, as will return or a double click.  Cursor keys, Page
Up/Down, mouse selection, and the scroll wheel all operate on the ACW.

“Hidden” attributes can be accessed by typing the beginning of hidden
name after a ‘.’, e.g. ‘_’. This allows access to modules with
"__all__" set, or to class-private attributes.

Completions and the ‘Expand Word’ facility can save a lot of typing!

Completions are currently limited to those in the namespaces. Names in
an Editor window which are not via "__main__" and "sys.modules" will
not be found.  Run the module once with your imports to correct this
situation. Note that IDLE itself places quite a few modules in
sys.modules, so much can be found by default, e.g. the re module.

If you don’t like the ACW popping up unbidden, simply make the delay
longer or disable the extension.


26.5.2.3. Calltips
------------------

A calltip is shown when one types "(" after the name of an
*accessible* function.  A name expression may include dots and
subscripts.  A calltip remains until it is clicked, the cursor is
moved out of the argument area, or ")" is typed.  When the cursor is
in the argument part of a definition, the menu or shortcut display a
calltip.

A calltip consists of the function signature and the first line of the
docstring.  For builtins without an accessible signature, the calltip
consists of all lines up the fifth line or the first blank line.
These details may change.

The set of *accessible* functions depends on what modules have been
imported into the user process, including those imported by Idle
itself, and what definitions have been run, all since the last
restart.

For example, restart the Shell and enter "itertools.count(".  A
calltip appears because Idle imports itertools into the user process
for its own use. (This could change.)  Enter "turtle.write(" and
nothing appears.  Idle does not import turtle.  The menu or shortcut
do nothing either.  Enter "import turtle" and then "turtle.write("
will work.

In an editor, import statements have no effect until one runs the
file.  One might want to run a file after writing the import
statements at the top, or immediately run an existing file before
editing.


26.5.2.4. Python Shell window
-----------------------------

* "C-c" interrupts executing command

* "C-d" sends end-of-file; closes window if typed at a ">>>" prompt

* "Alt-/" (Expand word) is also useful to reduce typing

  Command history

  * "Alt-p" retrieves previous command matching what you have typed.
    On OS X use "C-p".

  * "Alt-n" retrieves next. On OS X use "C-n".

  * "Return" while on any previous command retrieves that command


26.5.2.5. Text colors
---------------------

Idle defaults to black on white text, but colors text with special
meanings. For the shell, these are shell output, shell error, user
output, and user error.  For Python code, at the shell prompt or in an
editor, these are keywords, builtin class and function names, names
following "class" and "def", strings, and comments. For any text
window, these are the cursor (when present), found text (when
possible), and selected text.

Text coloring is done in the background, so uncolorized text is
occasionally visible.  To change the color scheme, use the Configure
IDLE dialog Highlighting tab.  The marking of debugger breakpoint
lines in the editor and text in popups and dialogs is not user-
configurable.


26.5.3. Startup and code execution
==================================

Upon startup with the "-s" option, IDLE will execute the file
referenced by the environment variables "IDLESTARTUP" or
"PYTHONSTARTUP". IDLE first checks for "IDLESTARTUP"; if "IDLESTARTUP"
is present the file referenced is run.  If "IDLESTARTUP" is not
present, IDLE checks for "PYTHONSTARTUP".  Files referenced by these
environment variables are convenient places to store functions that
are used frequently from the IDLE shell, or for executing import
statements to import common modules.

In addition, "Tk" also loads a startup file if it is present.  Note
that the Tk file is loaded unconditionally.  This additional file is
".Idle.py" and is looked for in the user’s home directory.  Statements
in this file will be executed in the Tk namespace, so this file is not
useful for importing functions to be used from IDLE’s Python shell.


26.5.3.1. Command line usage
----------------------------

   idle.py [-c command] [-d] [-e] [-h] [-i] [-r file] [-s] [-t title] [-] [arg] ...

   -c command  run command in the shell window
   -d          enable debugger and open shell window
   -e          open editor window
   -h          print help message with legal combinations and exit
   -i          open shell window
   -r file     run file in shell window
   -s          run $IDLESTARTUP or $PYTHONSTARTUP first, in shell window
   -t title    set title of shell window
   -           run stdin in shell (- must be last option before args)

If there are arguments:

* If "-", "-c", or "r" is used, all arguments are placed in
  "sys.argv[1:...]" and "sys.argv[0]" is set to "''", "'-c'", or
  "'-r'".  No editor window is opened, even if that is the default set
  in the Options dialog.

* Otherwise, arguments are files opened for editing and "sys.argv"
  reflects the arguments passed to IDLE itself.


26.5.3.2. Startup failure
-------------------------

IDLE uses a socket to communicate between the IDLE GUI process and the
user code execution process.  A connection must be established
whenever the Shell starts or restarts.  (The latter is indicated by a
divider line that says ‘RESTART’). If the user process fails to
connect to the GUI process, it displays a "Tk" error box with a
‘cannot connect’ message that directs the user here.  It then exits.

A common cause of failure is a user-written file with the same name as
a standard library module, such as *random.py* and *tkinter.py*. When
such a file is located in the same directory as a file that is about
to be run, IDLE cannot import the stdlib file.  The current fix is to
rename the user file.

Though less common than in the past, an antivirus or firewall program
may stop the connection.  If the program cannot be taught to allow the
connection, then it must be turned off for IDLE to work.  It is safe
to allow this internal connection because no data is visible on
external ports.  A similar problem is a network mis-configuration that
blocks connections.

Python installation issues occasionally stop IDLE: multiple versions
can clash, or a single installation might need admin access.  If one
undo the clash, or cannot or does not want to run as admin, it might
be easiest to completely remove Python and start over.

A zombie pythonw.exe process could be a problem.  On Windows, use Task
Manager to detect and stop one.  Sometimes a restart initiated by a
program crash or Keyboard Interrupt (control-C) may fail to connect.
Dismissing the error box or Restart Shell on the Shell menu may fix a
temporary problem.

When IDLE first starts, it attempts to read user configuration files
in ~/.idlerc/ (~ is one’s home directory).  If there is a problem, an
error message should be displayed.  Leaving aside random disk
glitches, this can be prevented by never editing the files by hand,
using the configuration dialog, under Options, instead Options.  Once
it happens, the solution may be to delete one or more of the
configuration files.

If IDLE quits with no message, and it was not started from a console,
try starting from a console ("python -m idlelib)" and see if a message
appears.


26.5.3.3. IDLE-console differences
----------------------------------

With rare exceptions, the result of executing Python code with IDLE is
intended to be the same as executing the same code in a console
window. However, the different interface and operation occasionally
affect visible results.  For instance, "sys.modules" starts with more
entries.

IDLE also replaces "sys.stdin", "sys.stdout", and "sys.stderr" with
objects that get input from and send output to the Shell window. When
Shell has the focus, it controls the keyboard and screen.  This is
normally transparent, but functions that directly access the keyboard
and screen will not work.  If "sys" is reset with
"importlib.reload(sys)", IDLE’s changes are lost and things like
"input", "raw_input", and "print" will not work correctly.

With IDLE’s Shell, one enters, edits, and recalls complete statements.
Some consoles only work with a single physical line at a time.  IDLE
uses "exec" to run each statement.  As a result, "'__builtins__'" is
always defined for each statement.


26.5.3.4. Developing tkinter applications
-----------------------------------------

IDLE is intentionally different from standard Python in order to
facilitate development of tkinter programs.  Enter "import tkinter as
tk; root = tk.Tk()" in standard Python and nothing appears.  Enter the
same in IDLE and a tk window appears.  In standard Python, one must
also enter "root.update()" to see the window.  IDLE does the
equivalent in the background, about 20 times a second, which is about
every 50 milleseconds. Next enter "b = tk.Button(root, text='button');
b.pack()".  Again, nothing visibly changes in standard Python until
one enters "root.update()".

Most tkinter programs run "root.mainloop()", which usually does not
return until the tk app is destroyed.  If the program is run with
"python -i" or from an IDLE editor, a ">>>" shell prompt does not
appear until "mainloop()" returns, at which time there is nothing left
to interact with.

When running a tkinter program from an IDLE editor, one can comment
out the mainloop call.  One then gets a shell prompt immediately and
can interact with the live application.  One just has to remember to
re-enable the mainloop call when running in standard Python.


26.5.3.5. Running without a subprocess
--------------------------------------

By default, IDLE executes user code in a separate subprocess via a
socket, which uses the internal loopback interface.  This connection
is not externally visible and no data is sent to or received from the
Internet. If firewall software complains anyway, you can ignore it.

If the attempt to make the socket connection fails, Idle will notify
you. Such failures are sometimes transient, but if persistent, the
problem may be either a firewall blocking the connection or
misconfiguration of a particular system.  Until the problem is fixed,
one can run Idle with the -n command line switch.

If IDLE is started with the -n command line switch it will run in a
single process and will not create the subprocess which runs the RPC
Python execution server.  This can be useful if Python cannot create
the subprocess or the RPC socket interface on your platform.  However,
in this mode user code is not isolated from IDLE itself.  Also, the
environment is not restarted when Run/Run Module (F5) is selected.  If
your code has been modified, you must reload() the affected modules
and re-import any specific items (e.g. from foo import baz) if the
changes are to take effect.  For these reasons, it is preferable to
run IDLE with the default subprocess if at all possible.

Deprecated since version 3.4.


26.5.4. Help and preferences
============================


26.5.4.1. Additional help sources
---------------------------------

IDLE includes a help menu entry called “Python Docs” that will open
the extensive sources of help, including tutorials, available at
docs.python.org. Selected URLs can be added or removed from the help
menu at any time using the Configure IDLE dialog. See the IDLE help
option in the help menu of IDLE for more information.


26.5.4.2. Setting preferences
-----------------------------

The font preferences, highlighting, keys, and general preferences can
be changed via Configure IDLE on the Option menu.  Keys can be user
defined; IDLE ships with four built-in key sets. In addition, a user
can create a custom key set in the Configure IDLE dialog under the
keys tab.


26.5.4.3. Extensions
--------------------

IDLE contains an extension facility.  Preferences for extensions can
be changed with the Extensions tab of the preferences dialog. See the
beginning of config-extensions.def in the idlelib directory for
further information.  The only current default extension is zzdummy,
an example also used for testing.
