PYTHON(1)                   General Commands Manual                  PYTHON(1)



NAME
       python  - an interpreted, interactive, object-oriented programming lan-
       guage

SYNOPSIS
       python [ -B ] [ -d ] [ -E ] [ -h ] [ -i ] [ -m module-name ]
              [ -O ] [ -OO ] [ -R ] [ -Q argument ] [ -s ] [ -S ] [ -t ] [  -u
       ]
              [ -v ] [ -V ] [ -W argument ] [ -x ] [ -3 ] [ -?  ]
              [ -c command | script | - ] [ arguments ]

DESCRIPTION
       Python is an interpreted, interactive, object-oriented programming lan-
       guage 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 (per-
       haps  too) much detail.  (These documents may be located via the INTER-
       NET RESOURCES below; they may be installed on your system as well.)

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

       Documentation  for  installed Python modules and packages can be viewed
       by running the pydoc program.

COMMAND LINE OPTIONS
       -B     Don't write .py[co] files on import. See  also  PYTHONDONTWRITE-
              BYTECODE.

       -c command
              Specify  the command to execute (see next section).  This termi-
              nates the option list (following options are passed as arguments
              to the command).

       -d     Turn  on parser debugging output (for wizards only, depending on
              compilation options).

       -E     Ignore environment variables like PYTHONPATH and PYTHONHOME that
              modify the behavior of the interpreter.

       -h ,  -? ,  --help
              Prints the usage for the interpreter executable and exits.

       -i     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.

       -m module-name
              Searches  sys.path for the named module and runs the correspond-
              ing .py file as a script.

       -O     Turn on basic optimizations.  This changes the  filename  exten-
              sion  for  compiled  (bytecode)  files from .pyc to .pyo.  Given
              twice, causes docstrings to be discarded.

       -OO    Discard docstrings in addition to the -O optimizations.

       -R     Turn on "hash randomization", so that the hash() values of  str,
              bytes  and  datetime  objects are "salted" with an unpredictable
              pseudo-random value.  Although they remain  constant  within  an
              individual  Python  process,  they  are  not predictable between
              repeated invocations of Python.

              This is intended to provide protection against a denial of  ser-
              vice  caused  by  carefully-chosen inputs that exploit the worst
              case performance of a dict construction, O(n^2) complexity.  See
              http://www.ocert.org/advisories/ocert-2011-003.html for details.

       -Q argument
              Division  control;  see  PEP  238.   The argument must be one of
              "old" (the default, int/int  and  long/long  return  an  int  or
              long), "new" (new division semantics, i.e. int/int and long/long
              returns a float), "warn" (old division semantics with a  warning
              for int/int and long/long), or "warnall" (old division semantics
              with a warning for all use of the division operator).  For a use
              of "warnall", see the Tools/scripts/fixdiv.py script.

       -s     Don't add user site directory to sys.path.

       -S     Disable  the  import  of  the module site and the site-dependent
              manipulations of sys.path that it entails.

       -t     Issue a warning when a source file mixes  tabs  and  spaces  for
              indentation  in a way that makes it depend on the worth of a tab
              expressed in spaces.  Issue an error when the  option  is  given
              twice.

       -u     Force  stdin,  stdout  and  stderr to be totally unbuffered.  On
              systems where it matters, also put stdin, stdout and  stderr  in
              binary  mode.   Note  that there is internal buffering in xread-
              lines(), readlines() and file-object  iterators  ("for  line  in
              sys.stdin")  which  is  not  influenced by this option.  To work
              around this, you will want to use "sys.stdin.readline()"  inside
              a "while 1:" loop.

       -v     Print  a  message each time a module is initialized, showing the
              place (filename or built-in module) from  which  it  is  loaded.
              When  given twice, print a message for each file that is checked
              for when searching for a module.  Also provides  information  on
              module cleanup at exit.

       -V ,  --version
              Prints the Python version number of the executable and exits.

       -W argument
              Warning  control.   Python  sometimes  prints warning message to
              sys.stderr.  A typical warning message has the  following  form:
              file:line:  category:  message.   By  default,  each  warning is
              printed once for each source line where it occurs.  This  option
              controls  how  often  warnings are printed.  Multiple -W options
              may be given; when a warning matches more than one  option,  the
              action  for  the  last matching option is performed.  Invalid -W
              options are ignored (a warning message is printed about  invalid
              options when the first warning is issued).  Warnings can also be
              controlled from within a Python program using the warnings  mod-
              ule.

              The  simplest  form  of  argument is one of the following action
              strings (or a unique abbreviation): ignore to ignore  all  warn-
              ings; default to explicitly request the default behavior (print-
              ing each warning once per source line); all to print  a  warning
              each  time it occurs (this may generate many messages if a warn-
              ing is triggered repeatedly for the same source  line,  such  as
              inside a loop); module to print each warning only the first time
              it occurs in each module; once to print each  warning  only  the
              first time it occurs in the program; or error to raise an excep-
              tion instead of printing a warning message.

              The  full  form  of  argument  is   action:message:category:mod-
              ule:line.   Here,  action is as explained above but only applies
              to messages that match the remaining fields.  Empty fields match
              all  values;  trailing empty fields may be omitted.  The message
              field matches the start of the  warning  message  printed;  this
              match is case-insensitive.  The category field matches the warn-
              ing category.  This must be a class name; the match test whether
              the  actual warning category of the message is a subclass of the
              specified warning category.  The full class name must be  given.
              The module field matches the (fully-qualified) module name; this
              match is case-sensitive.  The line field matches the  line  num-
              ber,  where zero matches all line numbers and is thus equivalent
              to an omitted line number.

       -x     Skip the first line of the source.  This is intended for  a  DOS
              specific hack only.  Warning: the line numbers in error messages
              will be off by one!

       -3     Warn about Python 3.x incompatibilities that 2to3  cannot  triv-
              ially fix.

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
       script  from  that  file;  when called with -c command, it executes the
       Python statement(s) given as command.  Here command may contain  multi-
       ple  statements  separated by newlines.  Leading whitespace is signifi-
       cant in Python statements!  In non-interactive mode, the  entire  input
       is parsed before 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 sys to be able to access it).  If no
       script name is given, sys.argv[0] is an empty string; if  -c  is  used,
       sys.argv[0] contains the string '-c'.  Note that options interpreted by
       the Python interpreter itself 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  KeyboardInterrupt
       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.

FILES AND DIRECTORIES
       These are subject to difference depending on local installation conven-
       tions; ${prefix}  and  ${exec_prefix}  are  installation-dependent  and
       should  be  interpreted  as for GNU software; they may be the same.  On
       Debian GNU/{Hurd,Linux} the default for both is /usr.

       ${exec_prefix}/bin/python
              Recommended location of the interpreter.

       ${prefix}/lib/python<version>
       ${exec_prefix}/lib/python<version>
              Recommended locations of the directories containing the standard
              modules.

       ${prefix}/include/python<version>
       ${exec_prefix}/include/python<version>
              Recommended  locations of the directories containing the include
              files needed for developing Python extensions and embedding  the
              interpreter.

       ~/.pythonrc.py
              User-specific initialization file loaded by the user module; not
              used by default or by most applications.

ENVIRONMENT VARIABLES
       PYTHONHOME
              Change the  location  of  the  standard  Python  libraries.   By
              default, the libraries are searched in ${prefix}/lib/python<ver-
              sion> and  ${exec_prefix}/lib/python<version>,  where  ${prefix}
              and  ${exec_prefix} are installation-dependent directories, both
              defaulting to /usr/local.  When $PYTHONHOME is set to  a  single
              directory, its value replaces both ${prefix} and ${exec_prefix}.
              To specify different values for these, set $PYTHONHOME to ${pre-
              fix}:${exec_prefix}.

       PYTHONPATH
              Augments  the  default search path for module files.  The format
              is the same as the shell's $PATH: one or  more  directory  path-
              names   separated   by  colons.   Non-existent  directories  are
              silently ignored.   The  default  search  path  is  installation
              dependent,  but  generally begins with ${prefix}/lib/python<ver-
              sion> (see PYTHONHOME above).  The default search path is always
              appended  to  $PYTHONPATH.   If  a script argument is given, the
              directory containing the script is inserted in the path in front
              of  $PYTHONPATH.  The search path can be manipulated from within
              a Python program as the variable sys.path.

       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 sys.ps1
              and sys.ps2 in this file.

       PYTHONY2K
              Set this to a non-empty string  to  cause  the  time  module  to
              require  dates  specified  as  strings to include 4-digit years,
              otherwise 2-digit years are converted based on  rules  described
              in the time module documentation.

       PYTHONOPTIMIZE
              If  this is set to a non-empty string it is equivalent to speci-
              fying the -O option. If set to an integer, it is  equivalent  to
              specifying -O multiple times.

       PYTHONDEBUG
              If  this is set to a non-empty string it is equivalent to speci-
              fying the -d option. If set to an integer, it is  equivalent  to
              specifying -d multiple times.

       PYTHONDONTWRITEBYTECODE
              If  this is set to a non-empty string it is equivalent to speci-
              fying the -B option (don't try to write .py[co] files).

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

       PYTHONIOENCODING
              If  this is set before running the interpreter, it overrides the
              encoding used for stdin/stdout/stderr, in the  syntax  encoding-
              name:errorhandler  The errorhandler part is optional and has the
              same meaning as in str.encode. For stderr, the errorhandler
               part is ignored; the handler will always be 'backslashreplace'.

       PYTHONNOUSERSITE
              If this is set to a non-empty string it is equivalent to  speci-
              fying  the  -s  option  (Don't  add  the  user site directory to
              sys.path).

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

       PYTHONVERBOSE
              If  this is set to a non-empty string it is equivalent to speci-
              fying the -v option. If set to an integer, it is  equivalent  to
              specifying -v multiple times.

       PYTHONWARNINGS
              If  this  is set to a comma-separated string it is equivalent to
              specifying the -W option for each separate value.

       PYTHONHASHSEED
              If this variable is set to "random", the effect is the  same  as
              specifying  the  -R  option:  a random value is used to seed the
              hashes of str, bytes and datetime objects.

              If PYTHONHASHSEED is set to an integer value, it is  used  as  a
              fixed seed for generating the hash() of the types covered by the
              hash randomization.  Its purpose is to allow repeatable hashing,
              such  as for selftests for the interpreter itself, or to allow a
              cluster of python processes to share hash values.

              The  integer  must  be   a   decimal   number   in   the   range
              [0,4294967295].   Specifying  the  value 0 will lead to the same
              hash values as when hash randomization is disabled.

AUTHOR
       The Python Software Foundation: http://www.python.org/psf

INTERNET RESOURCES
       Main website:  http://www.python.org/
       Documentation:  http://docs.python.org/
       Developer resources:  http://docs.python.org/devguide/
       Downloads:  http://python.org/download/
       Module repository:  http://pypi.python.org/
       Newsgroups:  comp.lang.python, comp.lang.python.announce

LICENSING
       Python is distributed under an  Open  Source  license.   See  the  file
       "LICENSE"  in the Python source distribution for information on terms &
       conditions for accessing and otherwise using  Python  and  for  a  DIS-
       CLAIMER OF ALL WARRANTIES.



                                    $Date$                           PYTHON(1)
