25.5. IDLE

IDLE is the Python IDE built with the tkinter GUI toolkit.

IDLE has the following features:

  • coded in 100% pure Python, using the tkinter GUI toolkit
  • cross-platform: works on Windows, Unix, and Mac OS X
  • multi-window text editor with multiple undo, Python colorizing, smart indent, call tips, and many other features
  • Python shell window (a.k.a. interactive interpreter)
  • debugger (not complete, but you can set breakpoints, view and step)

25.5.2. Editing and navigation

  • 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 backwards 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. 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. 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 name spaces, 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. Or another option is the delay could be set to zero. Another alternative to preventing ACW popups is to disable the call tips extension. Python Shell window

  • C-c interrupts executing command

  • C-d sends end-of-file; closes window if typed at a >>> prompt (this is C-z on Windows).

  • 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

25.5.3. Syntax colors

The coloring is applied in a background “thread,” so you may occasionally see uncolorized text. To change the color scheme, edit the [Colors] section in config.txt.

Python syntax colors:
Shell colors:
Console output
dark green

25.5.4. Startup

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. Command line usage

idle.py [-c command] [-d] [-e] [-s] [-t title] [arg] ...

-c command  run this command
-d          enable debugger
-e          edit mode; arguments are files to be edited
-s          run $IDLESTARTUP or $PYTHONSTARTUP first
-t title    set title of shell window

If there are arguments:

  1. If -e is used, arguments are files opened for editing and sys.argv reflects the arguments passed to IDLE itself.
  2. Otherwise, if -c is used, all arguments are placed in sys.argv[1:...], with sys.argv[0] set to '-c'.
  3. Otherwise, if neither -e nor -c is used, the first argument is a script which is executed with the remaining arguments in sys.argv[1:...] and sys.argv[0] set to the script name. If the script name is ‘-‘, no script is executed but an interactive Python session is started; the arguments are still available in sys.argv.

25.5.5. 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.

25.5.6. Other preferences

The font preferences, highlighting, keys, and general preferences can be changed via the Configure IDLE menu option. Be sure to note that 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.

25.5.7. Extensions

IDLE contains an extension facility. See the beginning of config-extensions.def in the idlelib directory for further information. The default extensions are currently:

  • FormatParagraph
  • AutoExpand
  • ZoomHeight
  • ScriptBinding
  • CallTips
  • ParenMatch
  • AutoComplete
  • CodeContext