python - an interpreted, interactive, object-oriented programming language


python [ X11-options ] [ -d ] [ -i ] [ -s ] [ -u ] [ -v ] [ -c command | script | - ] [ arguments ]


Python is an interpreted, interactive, object-oriented programming language that combines remarkable power with very clear syntax. For an introduction to programming in Python you are referred to the Python Tutorial. The Python Library Reference documents built-in and standard types, constants, functions and modules. Finally, the Python Reference Manual describes the syntax and semantics of the core language in (perhaps too) much detail.

Python's basic power can be extended with your own modules written in C or C++. On some (most?) systems such modules may be dynamically loaded. Python is also adaptable as an extension language for existing applications. See the internal documentation for hints.


Turn on parser debugging output (for wizards only, depending on compilation options).
When a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command. It does not read the $PYTHONSTARTUP file. This can be useful to inspect global variables or a stack trace when a script raises an exception.
Suppresses the automatic printing of expressions entered in interactive mode (useful when input is actually generated e.g. by Emacs).
Force stdout and stderr to be totally unbuffered.
Print a message each time a module is initialized, showing the place (filename or built-in module) from which it is loaded.
-c command
Specify the command to execute (see next section). This terminates the option list (following options are passed as arguments to the command).

When the interpreter is configured to contain the stdwin built-in module for use with the X window system, additional command line options common to most X applications are recognized (by STDWIN), e.g. -display displayname and -geometry widthxheight+x+y. The complete set of options is described in the STDWIN documentation.


The interpreter interface resembles that of the UNIX shell: when called with standard input connected to a tty device, it prompts for commands and executes them until an EOF is read; when called with a file name argument or with a file as standard input, it reads and executes a script from that file; when called with -c command, it executes the Python statement(s) given as command. Here command may contain multiple statements separated by newlines. Leading whitespace is significant in Python statements! In non-interactive mode, the entire input is parsed befored it is executed.

If available, the script name and additional arguments thereafter are passed to the script in the Python variable sys.argv which is a list of strings (you must first import to be able to access it). If no script name is given, sys.argv is empty; if -c is used, sys.argv[0] contains the string '-c'. Note that options interpreter by the Python interpreter or by STDWIN are not placed in sys.argv.

In interactive mode, the primary prompt is `>>>'; the second prompt (which appears when a command is not complete) is `...'. The prompts can be changed by assignment to sys.ps1 or sys.ps2. The interpreter quits when it reads an EOF at a prompt. When an unhandled exception occurs, a stack trace is printed and control returns to the primary prompt; in non-interactive mode, the interpreter exits after printing the stack trace. The interrupt signal raises the Keyboard\%Interrupt exception; other UNIX signals are not caught (except that SIGPIPE is sometimes ignored, in favor of the IOError exception). Error messages are written to stderr.


These are subject to difference depending on local installation conventions:

Recommended location of the interpreter.

Recommended location of the directory containing the standard modules.


Augments the default search path for module files. The format is the same as the shell's $PATH: one or more directory pathnames separated by colons. Non-existant directories are silently ignored. The default search path is installation dependent, but always begins with `.', (for example, .:/usr/local/lib/python The default search path is appended to $PYTHONPATH. The search path can be manipulated from within a Python program as the variable sys.path

If this is the name of a readable file, the Python commands in that file are executed before the first prompt is displayed in interactive mode. The file is executed in the same name space where interactive commands are executed so that objects defined or imported in it can be used without qualification in the interactive session. You can also change the prompts sys.ps1 and sys.ps2 in this file.

If this is set to a non-empty string it is equivalent to specifying the -d option.

If this is set to a non-empty string it is equivalent to specifying the -i option.

If this is set to a non-empty string it is equivalent to specifying the -s option.

If this is set to a non-empty string it is equivalent to specifying the -u option.

If this is set to a non-empty string it is equivalent to specifying the -v option.


Python Tutorial

Python Library Reference

Python Reference Manual

STDWIN under X11


The first time stdwin is imported, it initializes the STDWIN library. If this initialization fails, e.g. because the display connection fails, the interpreter aborts immediately.


Guido van Rossum
CWI (Centrum voor Wiskunde en Informatica)
P.O. Box 4079
1009 AB  Amsterdam
The Netherlands



There is a mailing list devoted to Python programming, bugs and design. To subscribe, send mail containing your real name and e-mail address in Internet form to


Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam, The Netherlands.

All Rights Reserved

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the names of Stichting Mathematisch Centrum or CWI not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.