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PYTHON(1)                            General Commands Manual                            PYTHON(1)

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

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 language that combines
       remarkable power with very clear syntax.  For an introduction to  programming  in  Python,
       see  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.  (These docu-
       ments may be located via the INTERNET RESOURCES below; they may be installed on your  sys-
       tem 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 applications.  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 PYTHONDONTWRITEBYTECODE.

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

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

       -E     Ignore environment variables like PYTHONPATH and PYTHONHOME that modify the  behav-
              ior 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 interac-
              tive mode after executing the script or the command.  It does not read the $PYTHON-
              STARTUP 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 corresponding  .py  file  as  a
              script.

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

       -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  re-
              main 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 service caused by  care-
              fully-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 de-
              tails.

       -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 warn-
              ing 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 mat-
              ters, also put stdin, stdout and stderr in binary mode.  Note that there is  inter-
              nal  buffering in xreadlines(), 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 informa-
              tion 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 in-
              valid options when the first warning is issued).  Warnings can also  be  controlled
              from within a Python program using the warnings module.

              The  simplest  form of argument is one of the following action strings (or a unique
              abbreviation): ignore to ignore all warnings; default to explicitly request the de-
              fault behavior (printing each warning once per source line); all to print a warning
              each time it occurs (this may generate many messages if a warning is triggered  re-
              peatedly  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 exception in-
              stead of printing a warning message.

              The full form of argument is action:message:category:module: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-insensi-
              tive.  The category field matches the warning 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 number, 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 trivially fix.

INTERPRETER INTERFACE
       The interpreter interface resembles that of the UNIX shell: when called with standard  in-
       put  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 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  ex-
       ception  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 conventions; ${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<version>  and  ${exec_prefix}/lib/python<ver-
              sion>,  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 ${prefix}:${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 pathnames separated by colons.  Non-existent
              directories are silently ignored.  The default search path is  installation  depen-
              dent,  but  generally  begins  with  ${prefix}/lib/python<version>  (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 pro-
              gram as the variable sys.path.

       PYTHONSTARTUP
              If  this  is the name of a readable file, the Python commands in that file are exe-
              cuted before the first prompt is displayed in interactive mode.  The file  is  exe-
              cuted  in  the  same name space where interactive commands are executed so that ob-
              jects defined or imported in it can be used without qualification in  the  interac-
              tive 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 specifying 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 specifying 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 specifying 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 specifying the -i option.

       PYTHONIOENCODING
              If this is set before running the interpreter, it overrides the encoding  used  for
              stdin/stdout/stderr,  in the syntax encodingname: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 specifying 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 specifying the -u option.

       PYTHONVERBOSE
              If  this is set to a non-empty string it is equivalent to specifying 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  ob-
              jects.

              If PYTHONHASHSEED is set to an integer value, it is used as a fixed seed for gener-
              ating 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: https://www.python.org/psf/

INTERNET RESOURCES
       Main website:  https://www.python.org/
       Documentation:   file:///usr/share/doc/python2.7/html/index.html  (python-doc  package) or
       https://docs.python.org/2/
       Developer resources:  https://docs.python.org/devguide/
       Downloads:  https://www.python.org/downloads/
       Module repository:  https://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 us-
       ing Python and for a DISCLAIMER OF ALL WARRANTIES.

                                                                                        PYTHON(1)

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