PYTHON(1)                   General Commands Manual                  PYTHON(1)

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

       python [ -B ] [ -b ] [ -d ] [ -E ] [ -h ] [ -i ] [ -I ]
              [ -m module-name ] [ -q ] [ -O ] [ -OO ] [ -s ] [ -S ] [ -u ]
              [ -v ] [ -V ] [ -W argument ] [ -x ] [ [ -X option ] -?  ]
              [ -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, see the  Python  Tutorial.   The
       Python  Library  Reference  documents built-in and standard types, con-
       stants, 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 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 .pyc files on import. See also PYTHONDONTWRITEBYTE-

       -b     Issue   warnings    about    str(bytes_instance),    str(bytear-
              ray_instance)  and  comparing  bytes/bytearray  with  str. (-bb:
              issue errors)

       -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.

       -I     Run Python in isolated mode. This also implies  -E  and  -s.  In
              isolated  mode  sys.path contains neither the script's directory
              nor the user's site-packages directory. All PYTHON*  environment
              variables are ignored, too.  Further restrictions may be imposed
              to prevent the user from injecting malicious code.

       -m module-name
              Searches sys.path for the named module and runs the  correspond-
              ing .py file as a script.

       -O     Remove  assert  statements and any code conditional on the value
              of __debug__; augment the filename for compiled (bytecode) files
              by adding .opt-1 before the .pyc extension.

       -OO    Do  -O and also discard docstrings; change the filename for com-
              piled (bytecode) files by adding .opt-2 before the  .pyc  exten-

       -q     Do  not print the version and copyright messages. These messages
              are also suppressed in non-interactive mode.

       -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.  Also disable these
              manipulations if site is explicitly imported later.

       -u     Force  the  binary  I/O  layers  of  stdout  and  stderr  to  be
              unbuffered.   stdin is always buffered.  The text I/O layer will
              still be line-buffered.

       -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.
              When given twice, print more information about the build.

       -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 option
              Set implementation specific option.

       -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!

       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.   On
       Debian GNU/{Hurd,Linux} the default for both is /usr.

              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

              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.

              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 .pyc 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", 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 disable hash ran-

       The Python Software Foundation:

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       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-

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