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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
       documents may be located via the INTERNET 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 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
              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 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
              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  service  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  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
              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 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
              default  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  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
              exception instead 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-
              insensitive.  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
       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 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 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<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
              ${prefix}:${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
              dependent, 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
              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 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
              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: https://www.python.org/psf/

INTERNET RESOURCES

       Main website:  https://www.python.org/
       Documentation:  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
       using Python and for a DISCLAIMER OF ALL WARRANTIES.

                                                                                        PYTHON(1)