NAME
       python - an interpreted, interactive, object-oriented programming language

SYNOPSIS
       python [ -B ] [ -b ] [ -d ] [ -E ] [ -h ] [ -i ] [ -I ]
              [ -m module-name ] [ -q ] [ -O ] [ -OO ] [ -s ] [ -S ] [ -u ]
              [ -v ] [ -V ] [ -W argument ] [ -x ] [ [ -X option ] -?  ]
              [ --check-hash-based-pycs default | always | never ]
              [ -c command | script | - ] [ arguments ]

PYTHON(1)                                      General Commands Manual                                      PYTHON(1)

NAME
       python - an interpreted, interactive, object-oriented programming language

SYNOPSIS
       python [ -B ] [ -b ] [ -d ] [ -E ] [ -h ] [ -i ] [ -I ]
              [ -m module-name ] [ -q ] [ -O ] [ -OO ] [ -s ] [ -S ] [ -u ]
              [ -v ] [ -V ] [ -W argument ] [ -x ] [ [ -X option ] -?  ]
              [ --check-hash-based-pycs default | always | never ]
              [ -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 .pyc files on import. See also PYTHONDONTWRITEBYTECODE.

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

       -c command
              Specify  the command to execute (see next section).  This terminates the option list (following options
              are passed as arguments to the command).

       --check-hash-based-pycs mode
              Configure how Python evaluates the up-to-dateness of hash-based .pyc files.

       -d     Turn on parser debugging output (for expert only, depending on compilation options).

       -E     Ignore environment variables like PYTHONPATH and PYTHONHOME that modify  the  behavior  of  the  inter‐
              preter.

       -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 exe‐
              cuting the script or the command.  It does not read the $PYTHONSTARTUP file.  This can be useful to in‐
              spect 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 corresponding .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 compiled (bytecode) files by  adding  .opt-2
              before the .pyc extension.

       -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 stdout and stderr streams to be unbuffered.  This option has no effect on the stdin stream.

       -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 warn‐
              ings 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 option
              Set implementation specific option. The following options are available:

                  -X faulthandler: enable faulthandler

                  -X showrefcount: output the total reference count and number of used
                      memory blocks when the program finishes or after each statement in the
                      interactive interpreter. This only works on debug builds

                  -X tracemalloc: start tracing Python memory allocations using the
                      tracemalloc module. By default, only the most recent frame is stored in a
                      traceback of a trace. Use -X tracemalloc=NFRAME to start tracing with a
                      traceback limit of NFRAME frames

                  -X importtime: show how long each import takes. It shows module name,
                      cumulative time (including nested imports) and self time (excluding
                      nested imports). Note that its output may be broken in multi-threaded
                      application. Typical usage is python3 -X importtime -c 'import asyncio'

                  -X dev: enable CPython's "development mode", introducing additional runtime
                      checks which are too expensive to be enabled by default. It will not be
                      more verbose than the default if the code is correct: new warnings are
                      only emitted when an issue is detected. Effect of the developer mode:
                         * Add default warning filter, as -W default
                         * Install debug hooks on memory allocators: see the PyMem_SetupDebugHooks() C function
                         * Enable the faulthandler module to dump the Python traceback on a crash
                         * Enable asyncio debug mode
                         * Set the dev_mode attribute of sys.flags to True
                         * io.IOBase destructor logs close() exceptions

                  -X utf8: enable UTF-8 mode for operating system interfaces, overriding the default
                      locale-aware mode. -X utf8=0 explicitly disables UTF-8 mode (even when it would
                      otherwise activate automatically). See PYTHONUTF8 for more details

                  -X pycache_prefix=PATH: enable writing .pyc files to a parallel tree rooted at the
                       given directory instead of to the code tree.

       -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!

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 in‐
       put is parsed before it is executed.

       If available, the script name and additional arguments thereafter are passed to the script in the Python vari‐
       able  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 com‐
       plete) 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 in‐
       terrupt  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  ex‐
              tensions and embedding the interpreter.

ENVIRONMENT VARIABLES
       PYTHONHOME
              Change the location of the standard Python libraries.  By default, the libraries are searched in ${pre‐
              fix}/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  de‐
              fault  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  argu‐
              ment  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.

       PYTHONPLATLIBDIR
              Override sys.platlibdir.

       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.

       PYTHONOPTIMIZE
              If  this  is set to a non-empty string it is equivalent to specifying the -O option. If set to an inte‐
              ger, 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  inte‐
              ger, 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
              .pyc 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 inte‐
              ger, 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  sepa‐
              rate value.

       PYTHONHASHSEED
              If  this  variable  is  set to "random", a random value is used to seed the hashes of str and bytes ob‐
              jects.

              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 randomization.

       PYTHONMALLOC
              Set the Python memory allocators and/or install debug hooks. The available memory allocators are malloc
              and pymalloc.  The available debug hooks are debug, malloc_debug, and pymalloc_debug.

              When Python is compiled in debug mode, the default is pymalloc_debug and the debug hooks are  automati‐
              cally used. Otherwise, the default is pymalloc.

       PYTHONMALLOCSTATS
              If  set to a non-empty string, Python will print statistics of the pymalloc memory allocator every time
              a new pymalloc object arena is created, and on shutdown.

              This variable is ignored if the $PYTHONMALLOC environment variable is used to force the malloc(3) allo‐
              cator of the C library, or if Python is configured without pymalloc support.

       PYTHONASYNCIODEBUG
              If this environment variable is set to a non-empty string, enable the debug mode of the asyncio module.

       PYTHONTRACEMALLOC
              If  this environment variable is set to a non-empty string, start tracing Python memory allocations us‐
              ing the tracemalloc module.

              The value of the variable is the maximum number of frames stored in a traceback of a trace.  For  exam‐
              ple, PYTHONTRACEMALLOC=1 stores only the most recent frame.

       PYTHONFAULTHANDLER
              If  this environment variable is set to a non-empty string, faulthandler.enable() is called at startup:
              install a handler for SIGSEGV, SIGFPE, SIGABRT, SIGBUS and SIGILL signals to dump the Python traceback.

              This is equivalent to the -X faulthandler option.

       PYTHONEXECUTABLE
              If this environment variable is set, sys.argv[0] will be set to its value  instead  of  the  value  got
              through the C runtime. Only works on Mac OS X.

       PYTHONUSERBASE
              Defines  the user base directory, which is used to compute the path of the user site-packages directory
              and Distutils installation paths for python setup.py install --user.

       PYTHONPROFILEIMPORTTIME
              If this environment variable is set to a non-empty string, Python will show how long each import takes.
              This is exactly equivalent to setting -X importtime on the command line.

       PYTHONBREAKPOINT
              If  this  environment  variable  is  set  to  0, it disables the default debugger. It can be set to the
              callable of your debugger of choice.

   Debug-mode variables
       Setting these variables only has an effect in a debug build of Python, that is, if Python was configured  with
       the --with-pydebug build option.

       PYTHONTHREADDEBUG
              If this environment variable is set, Python will print threading debug info.

       PYTHONDUMPREFS
              If  this  environment  variable is set, Python will dump objects and reference counts still alive after
              shutting down the interpreter.

AUTHOR
       The Python Software Foundation: https://www.python.org/psf/

INTERNET RESOURCES
       Main website:  https://www.python.org/
       Documentation:  https://docs.python.org/
       Developer resources:  https://devguide.python.org/
       Downloads:  https://www.python.org/downloads/
       Module repository:  https://pypi.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)