IDLE is Python’s Integrated Development and Learning Environment.
24.6.2. 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 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.
24.6.2.1. 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.
24.6.2.2. 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 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.
24.6.2.3. Calltips
A calltip is shown when one types ( after the name of an acccessible
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.
24.6.2.4. 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
24.6.2.5. 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.
24.6.3. 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.
24.6.3.1. 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 combinatios 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.
24.6.3.2. IDLE-console differences
As much as possible, the result of executing Python code with IDLE is the
same as executing the same code in a console window. However, the different
interface and operation occasionally affects results.
For instance, IDLE normally executes user code in a separate process from
the IDLE GUI itself. The IDLE versions of sys.stdin, .stdout, and .stderr in the
execution process get input from and send output to the GUI process,
which keeps control of the keyboard and screen. This is normally transparent,
but code that access these object will see different attribute values.
Also, functions that directly access the keyboard and screen will not work.
With IDLE’s Shell, one enters, edits, and recalls complete statements.
Some consoles only work with a single physical line at a time.
24.6.3.3. 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 connecton 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.
