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PYTHON(1)							     PYTHON(1)

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

SYNOPSIS
       python [ -B ] [ -d ] [ -E ] [ -h ] [ -i ] [ -m module-name ]
	      [ -O ] [ -O0 ] [ -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.

       -O0    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 insertion,  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.

       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.

       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://www.python.org/dev/
       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: 2010-01-31 11:09:16 -0500 (Sun, 31 Jan 2010) $   PYTHON(1)
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