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 PYTHON(1)                                                         PYTHON(1)

      python - an interpreted, interactive, object-oriented programming

      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 ]

      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

      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.

      -B   Don't write .py[co] files on import. See also

      -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

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 PYTHON(1)                                                         PYTHON(1)

           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
  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/ 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

      -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.

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 PYTHON(1)                                                         PYTHON(1)

      -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: 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: 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!

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 PYTHON(1)                                                         PYTHON(1)

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

      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.

      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.
      The default for both is /usr/local.

           Recommended location of the interpreter.

           Recommended locations of the directories containing the standard

           Recommended locations of the directories containing the include
           files needed for developing Python extensions and embedding the

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 PYTHON(1)                                                         PYTHON(1)

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

           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

           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.

           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.

           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.

           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.

           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

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 PYTHON(1)                                                         PYTHON(1)

           to specifying -d multiple times.

           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).

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

           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
            part is ignored; the handler will always be 'backslashreplace'.

           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

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

           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.

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

           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.

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 PYTHON(1)                                                         PYTHON(1)

      The Python Software Foundation:

      Main website:
      Developer resources:
      Module repository:
      Newsgroups:  comp.lang.python, comp.lang.python.announce

      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

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