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PYTHON(1)                                                                                          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 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  (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  xread-lines(), xreadlines(),
              lines(),  readlines()  and file-object iterators ("for line in sys.stdin") which is not influ-enced influenced
              enced 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 warn-ing warning
              ing  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  abbrevia-tion): abbreviation):
              tion):  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[_] is an empty string; if -c is used, sys.argv[_] 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 inter-preter interpreter
       preter 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 excep-tion). exception).
       tion).  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.  The default for both is /usr/local.

       ${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_pre-fix}. ${exec_prefix}.
              fix}.  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/std-out/stderr, stdin/stdout/stderr,
              out/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.

INTERACTIVE INPUT EDITING AND HISTORY SUBSTITUTION
       The Python inteterpreter supports editing of the current input line and history substitution, similar
       to facilities found in the Korn shell and the GNU Bash shell.  However, rather than being implemented
       using  the  GNU  Readline  library, this Python interpreter uses the BSD EditLine library editline(3)
       with a GNU Readline emulation layer.

       The readline module provides the access to the EditLine library, but there are a  few  major  differ-ences differences
       ences compared to a traditional implementation using the Readline library.  The command language used
       in the preference files is that of EditLine, as described in editrc(5) and not that used by the Read-line Readline
       line  library.   This  also means that the parse_and_bind() routines uses EditLine commands.  And the
       preference file itself is ~/.editrc instead of ~/.inputrc.

       For example, the rlcompleter module, which defines a completion function for  the  readline  modules,
       works correctly with the EditLine libraries, but needs to be initialized somewhat differently:

              import rlcompleter
              import readline
              readline.parse_and_bind("bind ^I rl_complete")

       For vi mode, one needs:

              readline.parse_and_bind("bind -v")

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 dis-tribution distribution
       tribution for information on terms & conditions for accessing and otherwise using Python  and  for  a
       DISCLAIMER OF ALL WARRANTIES.



                                                   $Date$                                          PYTHON(1)