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PYTHON(1)		    General Commands Manual		     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, 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 RE-
       SOURCES 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 re-
	      peated 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 ma-
	      nipulations of sys.path that it entails.

       -t     Issue a warning when a source file mixes tabs and	spaces for in-
	      dentation	 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 ex-
       ception;	 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  de-
	      fault,  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  de-
	      pendent, but generally begins with ${prefix}/lib/python<version>
	      (see PYTHONHOME above).  The default search path is  always  ap-
	      pended  to  $PYTHONPATH.	If a script argument is	given, the di-
	      rectory 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  in-
	      teractive	 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  re-
	      quire  dates specified as	strings	to include 4-digit years, oth-
	      erwise 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 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  "LI-
       CENSE"  in  the	Python	source distribution for	information on terms &
       conditions for accessing	and otherwise using  Python  and  for  a  DIS-



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