python2(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  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)





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