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PYTHON(1)                                                            PYTHON(1)


       python  - an interpreted, interactive, object-oriented programming lan-


       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 lan-
       guage 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 (per-
       haps  too) much detail.  (These documents may be located via the INTER-
       NET 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 applica-
       tions.  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  PYTHONDONTWRITE-

       -c command
              Specify  the command to execute (see next section).  This termi-
              nates 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 correspond-
              ing .py file as a script.

       -O     Turn on basic optimizations.  This changes the  filename  exten-
              sion  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  ser-
              vice  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  xread-
              lines(),  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 mod-

              The simplest form of argument is one  of  the  following  action
              strings  (or  a unique abbreviation): ignore to ignore all warn-
              ings; default to explicitly request the default behavior (print-
              ing  each  warning once per source line); all to print a warning
              each time it occurs (this may generate many messages if a  warn-
              ing  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 excep-
              tion instead of printing a warning message.

              The   full  form  of  argument  is  action:message:category:mod-
              ule: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 warn-
              ing 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 num-
              ber, 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 triv-
              ially 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 multi-
       ple statements separated by newlines.  Leading whitespace  is  signifi-
       cant  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 conven-
       tions;  ${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

              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<ver-
              sion>  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 ${pre-

              Augments the default search path for module files.   The  format
              is  the  same  as the shell's $PATH: one or more directory path-
              names  separated  by  colons.   Non-existent   directories   are
              silently  ignored.   The  default  search  path  is installation
              dependent, but generally begins  with  ${prefix}/lib/python<ver-
              sion> (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  speci-
              fying  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  speci-
              fying  the  -d option. If set to an integer, it is equivalent to
              specifying -d multiple times.

              If this is set to a non-empty string it is equivalent to  speci-
              fying the -B option (don't try to write .py[co] files).

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

              If this is set before running the interpreter, it overrides  the
              encoding  used  for stdin/stdout/stderr, in the syntax encoding-
              name: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'.

              If this is set to a non-empty string it is equivalent to  speci-
              fying  the  -s  option  (Don't  add  the  user site directory to

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

              If  this is set to a non-empty string it is equivalent to speci-
              fying 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.


       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 differences compared to a traditional implementa-
       tion 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  Readline  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  func-
       tion  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")


       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  DIS-

                                    $Date$                           PYTHON(1)

Mac OS X 10.9 - Generated Sun Oct 13 09:56:29 CDT 2013
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