+ +
+

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 macOS
    • +
  • 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
    • +
+ +
+

Editing and navigation¶

+
+

Editor windows¶

+

IDLE may open editor windows when it starts, depending on settings +and how you start IDLE. Thereafter, use the File menu. There can be only +one open editor window for a given file.

+

The title bar contains the name of the file, the full path, and the version +of Python and IDLE running the window. The status bar contains the line +number (‘Ln’) and column number (‘Col’). Line numbers start with 1; +column numbers with 0.

+

IDLE assumes that files with a known .py* extension contain Python code +and that other files do not. Run Python code with the Run menu.

+
+
+

Key bindings¶

+

In this section, ‘C’ refers to the Control key on Windows and Unix and +the Command key on macOS.

+
    +

  • 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.

+
+
+

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 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.

+
+
+

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.

+
+
+

Python Shell window¶

+

With IDLE’s Shell, one enters, edits, and recalls complete statements. +Most consoles and terminals only work with a single physical line at a time.

+

When one pastes code into Shell, it is not compiled and possibly executed +until one hits Return. One may edit pasted code first. +If one pastes more that one statement into Shell, the result will be a +SyntaxError when multiple statements are compiled as if they were one.

+

The editing features described in previous subsections work when entering +code interactively. IDLE’s Shell window also responds to the following keys.

+
    +

  • 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 +macOS use C-p.
      • +
    • Alt-n retrieves next. On macOS use C-n.
      • +
    • Return while on any previous command retrieves that command
      • +
    +
    • +
+
+
+

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.

+
+
+
+

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.

+
+

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.
    • +
+
+
+

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.

+
+
+

Running user code¶

+

With rare exceptions, the result of executing Python code with IDLE is +intended to be the same as executing the same code by the default method, +directly with Python in a text-mode system console or terminal window. +However, the different interface and operation occasionally affect +visible results. For instance, sys.modules starts with more entries, +and threading.activeCount() returns 2 instead of 1.

+

By default, IDLE runs user code in a separate OS process rather than in +the user interface process that runs the shell and editor. In the execution +process, it replaces sys.stdin, sys.stdout, and sys.stderr +with objects that get input from and send output to the Shell window. +The original values stored in sys.__stdin__, sys.__stdout__, and +sys.__stderr__ are not touched, but may be None.

+

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. These include system-specific functions that +determine whether a key has been pressed and if so, which.

+

IDLE’s standard stream replacements are not inherited by subprocesses +created in the execution process, whether directly by user code or by modules +such as multiprocessing. If such subprocess use input from sys.stdin +or print or write to sys.stdout or sys.stderr, +IDLE should be started in a command line window. The secondary subprocess +will then be attached to that window for input and output.

+

If sys is reset by user code, such as with importlib.reload(sys), +IDLE’s changes are lost and input from the keyboard and output to the screen +will not work correctly.

+
+
+

User output in Shell¶

+

When a program outputs text, the result is determined by the +corresponding output device. When IDLE executes user code, sys.stdout +and sys.stderr are connected to the display area of IDLE’s Shell. Some of +its features are inherited from the underlying Tk Text widget. Others +are programmed additions. Where it matters, Shell is designed for development +rather than production runs.

+

For instance, Shell never throws away output. A program that sends unlimited +output to Shell will eventually fill memory, resulting in a memory error. +In contrast, some system text windows only keep the last n lines of output. +A Windows console, for instance, keeps a user-settable 1 to 9999 lines, +with 300 the default.

+

Text widgets display a subset of Unicode, the Basic Multilingual Plane (BMP). +Which characters get a proper glyph instead of a replacement box depends on +the operating system and installed fonts. Newline characters cause following +text to appear on a new line, but other control characters are either +replaced with a box or deleted. However, repr(), which is used for +interactive echo of expression values, replaces control characters, +some BMP codepoints, and all non-BMP characters with escape codes +before they are output.

+

Normal and error output are generally kept separate (on separate lines) +from code input and each other. They each get different highlight colors.

+

For SyntaxError tracebacks, the normal ‘^’ marking where the error was +detected is replaced by coloring the text with an error highlight. +When code run from a file causes other exceptions, one may right click +on a traceback line to jump to the corresponding line in an IDLE editor. +The file will be opened if necessary.

+

Shell has a special facility for squeezing output lines down to a +‘Squeezed text’ label. This is done automatically +for output over N lines (N = 50 by default). +N can be changed in the PyShell section of the General +page of the Settings dialog. Output with fewer lines can be squeezed by +right clicking on the output. This can be useful lines long enough to slow +down scrolling.

+

Squeezed output is expanded in place by double-clicking the label. +It can also be sent to the clipboard or a separate view window by +right-clicking the label.

+
+
+

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.

+
+
+

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.

+
+
+
+
+

Help and preferences¶

+
+

Help sources¶

+

Help menu entry “IDLE Help†displays a formatted html version of the +IDLE chapter of the Library Reference. The result, in a read-only +tkinter text window, is close to what one sees in a web browser. +Navigate through the text with a mousewheel, +the scrollbar, or up and down arrow keys held down. +Or click the TOC (Table of Contents) button and select a section +header in the opened box.

+

Help menu entry “Python Docs†opens the extensive sources of help, +including tutorials, available at docs.python.org/x.y, where ‘x.y’ +is the currently running Python version. If your system +has an off-line copy of the docs (this may be an installation option), +that will be opened instead.

+

Selected URLs can be added or removed from the help menu at any time using the +General tab of the Configure IDLE dialog .

+
+
+

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.

+
+
+

IDLE on macOS¶

+

Under System Preferences: Dock, one can set “Prefer tabs when opening +documents†to “Alwaysâ€. This setting is not compatible with the tk/tkinter +GUI framework used by IDLE, and it breaks a few IDLE features.

+
+
+

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.

+
+
+
+ + +