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
- 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
25.5.3. Startup and code execution
Upon startup with the
-s option, IDLE will execute the file referenced by
the environment variables
IDLE first checks for
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.
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.
188.8.131.52. 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:
ris used, all arguments are placed in
sys.argvis set to
'-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.argvreflects the arguments passed to IDLE itself.
184.108.40.206. 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
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.
220.127.116.11. 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
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
IDLE’s changes are lost and things like
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.
18.104.22.168. 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.
b = tk.Button(root, text='button'); b.pack(). Again,
nothing visibly changes in standard Python until one enters
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
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.
22.214.171.124. 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.
25.5.4. Help and preferences
126.96.36.199. 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.
188.8.131.52. 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 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.