.TH PYTHON "3 January 1994"
.SH NAME
python \- an interpreted, interactive, object-oriented programming language
.SH SYNOPSIS
.B python
[
.I X11-options
]
[
.B \-d
]
[
.B \-i
]
[
.B \-k
]
[
.B \-v
]
[
.B \-c
.I command
|
.I script
|
\-
]
[
.I arguments
]
.SH DESCRIPTION
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.
.PP
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.
.SH COMMAND LINE OPTIONS
.TP
.B \-d
Turn on parser debugging output (for wizards only, depending on
compilation options).
.TP
.B \-i
When a script is passed as first argument or the \fB\-c\fP 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.
.TP
.B \-k
This hack, eh, feature is intended to help you to find expression
statements that print a value.  Although a feature of the language, it
can sometimes be annoying that when a function is called which returns
a value that is not
.IR None ,
the value is printed to standard output, and it is not always easy to
find which statement is the cause of an unwanted `1', for instance.
When this option is set, if an expression statement prints its value,
the exception
.I RuntimeError
is raised.  The resulting stack trace will help you to track down the
culprit.
.TP
.B \-v
Print a message each time a module is initialized, showing the place
(filename or built-in module) from which it is loaded.
.TP
.BI "\-c " command
Specify the command to execute (see next section).
This terminates the option list (following options are passed as
arguments to the command).
.PP
When the interpreter is configured to contain the
.I 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.
.B \-display
.I displayname
and
.B \-geometry
.I widthxheight+x+y.
The complete set of options is described in the STDWIN documentation.
.SH INTERPRETER INTERFACE
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
.I script
from that file;
when called with
.B \-c
.I command,
it executes the Python statement(s) given as
.I command.
Here
.I 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.
.PP
If available, the script name and additional arguments thereafter are
passed to the script in the Python variable
.I sys.argv ,
which is a list of strings (you must first
.I import sys
to be able to access it).
If no script name is given,
.I sys.argv
is empty; if
.B \-c
is used,
.I sys.argv[0]
contains the string
.I '-c'.
Note that options interpreter by the Python interpreter or by STDWIN
are not placed in
.I sys.argv.
.PP
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
.I sys.ps1
or
.I 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
.I Keyboard\%Interrupt
exception; other UNIX signals are not caught (except that SIGPIPE is
sometimes ignored, in favor of the
.I IOError
exception).  Error messages are written to stderr.
.SH FILES AND DIRECTORIES
These are subject to difference depending on local installation
conventions:
.IP /usr/local/bin/python
Recommended location of the interpreter.
.IP /usr/local/lib/python
Recommended location of the directory containing the standard modules.
.SH ENVIRONMENT VARIABLES
.IP PYTHONPATH
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,
.I .:/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
.I sys.path .
.IP PYTHONSTARTUP
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
.I sys.ps1
and
.I sys.ps2
in this file.
.IP PYTHONDEBUG
If this is set to a non-empty string it is equivalent to specifying
the \fB\-d\fP option.
.IP PYTHONINSPECT
If this is set to a non-empty string it is equivalent to specifying
the \fB\-i\fP option.
.IP PYTHONKILLPRINT
If this is set to a non-empty string it is equivalent to specifying
the \fB\-k\fP option.
.IP PYTHONVERBOSE
If this is set to a non-empty string it is equivalent to specifying
the \fB\-v\fP option.
.SH SEE ALSO
Python Tutorial
.br
Python Library Reference
.br
Python Reference Manual
.br
STDWIN under X11
.SH BUGS AND CAVEATS
The first time
.I stdwin
is imported, it initializes the STDWIN library.
If this initialization fails, e.g. because the display connection
fails, the interpreter aborts immediately.
.SH AUTHOR
.nf
Guido van Rossum
CWI (Centrum voor Wiskunde en Informatica)
P.O. Box 4079
1009 AB  Amsterdam
The Netherlands
.PP
E-mail: Guido.van.Rossum@cwi.nl
.fi
.SH MAILING LIST
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
.I python-list-request@cwi.nl.
.SH COPYRIGHT
Copyright 1991, 1992, 1993, 1994 by Stichting Mathematisch Centrum,
Amsterdam, The Netherlands.
.IP " "
All Rights Reserved
.PP
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.

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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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