.. moduleauthor:: Guido van Rossum <guido@python.org>
Source code: :source:`Lib/idlelib/`
.. index:: single: IDLE single: Python Editor single: Integrated Development Environment
IDLE is Python's Integrated Development and Learning Environment.
IDLE has the following features:
IDLE has two main window types, the Shell window and the Editor window. It is possible to have multiple editor windows simultaneously. On Windows and Linux, each has its own top menu. Each menu documented below indicates which window type it is associated with.
Output windows, such as used for Edit => Find in Files, are a subtype of editor window. They currently have the same top menu but a different default title and context menu.
On macOS, there is one application menu. It dynamically changes according to the window currently selected. It has an IDLE menu, and some entries described below are moved around to conform to Apple guidelines.
.. index:: single: Class browser single: Path browser
The clipboard functions are also available in context menus.
.. index:: single: Run script
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... index:: single: debugger single: stack viewer
Lists the names of all open windows; select one to bring it to the foreground (deiconifying it if necessary).
Additional help sources may be added here with the Configure IDLE dialog under the General tab. See the :ref:`Help sources <help-sources>` subsection below for more on Help menu choices.
.. index:: single: Cut single: Copy single: Paste single: Set Breakpoint single: Clear Breakpoint single: breakpoints
Open a context menu by right-clicking in a window (Control-click on macOS). Context menus have the standard clipboard functions also on the Edit menu.
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.
Shell and Output windows also have the following.
The Shell window also has an output squeezing facility explained in the Python Shell window subsection below.
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.
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.
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 on the :ref:`Format menu <format-menu>`.
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 :data:`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.
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.
Within an editor window containing Python code, code context can be toggled
in order to show or hide a pane at the top of the window. When shown, this
pane freezes the opening lines for block code, such as those beginning with
class, def, or if keywords, that would have otherwise scrolled
out of view. The size of the pane will be expanded and contracted as needed
to show the all current levels of context, up to the maximum number of
lines defined in the Configure IDLE dialog (which defaults to 15). If there
are no current context lines and the feature is toggled on, a single blank
line will display. Clicking on a line in the context pane will move that
line to the top of the editor.
The text and background colors for the context pane can be configured under the Highlights tab in the Configure IDLE dialog.
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 :exc:`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
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.
Upon startup with the -s option, IDLE will execute the file referenced by
the environment variables :envvar:`IDLESTARTUP` or :envvar:`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.
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:
-, -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.sys.argv reflects the arguments passed to IDLE itself.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.
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.
When user code raises SystemExit either directly or by calling sys.exit, IDLE returns to a Shell prompt instead of exiting.
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.
A Tk Text widget, and hence IDLE's Shell, displays characters (codepoints) in the BMP (Basic Multilingual Plane) subset of Unicode. Which characters are displayed with a proper glyph and which with a replacement box depends on the operating system and installed fonts. Tab characters cause the following text to begin after the next tab stop. (They occur every 8 'characters'). Newline characters cause following text to appear on a new line. Other control characters are ignored or displayed as a space, box, or something else, depending on the operating system and font. (Moving the text cursor through such output with arrow keys may exhibit some surprising spacing behavior.)
>>> s = 'a\tb\a<\x02><\r>\bc\nd' # Enter 22 chars. >>> len(s) 14 >>> s # Display repr(s) 'a\tb\x07<\x02><\r>\x08c\nd' >>> print(s, end='') # Display s as is. # Result varies by OS and font. Try it.
The repr function is used for interactive echo of expression
values. It returns an altered version of the input string in which
control codes, some BMP codepoints, and all non-BMP codepoints are
replaced with escape codes. As demonstrated above, it allows one to
identify the characters in a string, regardless of how they are displayed.
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.
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 milliseconds.
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.
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:: 3.4
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 .
The font preferences, highlighting, keys, and general preferences can be changed via Configure IDLE on the Option menu. 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.
On the Font tab, see the text sample for the effect of font face and size on multiple characters in multiple languages. Edit the sample to add other characters of personal interest. Use the sample to select monospaced fonts. If particular characters have problems in Shell or an editor, add them to the top of the sample and try changing first size and then font.
On the Highlights and Keys tab, select a built-in or custom color theme and key set. To use a newer built-in color theme or key set with older IDLEs, save it as a new custom theme or key set and it well be accessible to older IDLEs.
Under System Preferences: Dock, one can set "Prefer tabs when opening documents" to "Always". This setting is not compatible with the tk/tkinter GUI framework used by IDLE, and it breaks a few IDLE features.
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.
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