mirror of
https://github.com/python/cpython.git
synced 2024-12-11 10:50:11 +08:00
c6e5c1123b
Remove: * COUNT_ALLOCS macro * sys.getcounts() function * SHOW_ALLOC_COUNT code in listobject.c * SHOW_TRACK_COUNT code in tupleobject.c * PyConfig.show_alloc_count field * -X showalloccount command line option * @test.support.requires_type_collecting decorator
567 lines
18 KiB
Groff
567 lines
18 KiB
Groff
.TH PYTHON "1"
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.\" To view this file while editing, run it through groff:
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.\" groff -Tascii -man python.man | less
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.SH NAME
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python \- an interpreted, interactive, object-oriented programming language
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.SH SYNOPSIS
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.B python
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[
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.B \-B
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]
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[
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.B \-b
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]
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[
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.B \-d
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]
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[
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.B \-E
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]
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[
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.B \-h
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]
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[
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.B \-i
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]
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[
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.B \-I
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]
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.br
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[
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.B \-m
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.I module-name
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]
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[
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.B \-q
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]
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[
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.B \-O
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]
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[
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.B \-OO
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]
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[
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.B \-s
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]
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[
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.B \-S
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]
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[
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.B \-u
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]
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.br
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[
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.B \-v
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]
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[
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.B \-V
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]
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[
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.B \-W
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.I argument
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]
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[
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.B \-x
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]
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[
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[
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.B \-X
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.I option
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]
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.B \-?
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]
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.br
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[
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.B \--check-hash-based-pycs
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.I default
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|
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.I always
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|
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.I never
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]
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.br
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[
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.B \-c
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.I command
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|
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.I script
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|
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\-
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]
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[
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.I arguments
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]
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.SH DESCRIPTION
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Python is an interpreted, interactive, object-oriented programming
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language that combines remarkable power with very clear syntax.
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For an introduction to programming in Python, see the Python Tutorial.
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The Python Library Reference documents built-in and standard types,
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constants, functions and modules.
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Finally, the Python Reference Manual describes the syntax and
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semantics of the core language in (perhaps too) much detail.
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(These documents may be located via the
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.B "INTERNET RESOURCES"
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below; they may be installed on your system as well.)
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.PP
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Python's basic power can be extended with your own modules written in
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C or C++.
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On most systems such modules may be dynamically loaded.
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Python is also adaptable as an extension language for existing
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applications.
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See the internal documentation for hints.
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.PP
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Documentation for installed Python modules and packages can be
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viewed by running the
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.B pydoc
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program.
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.SH COMMAND LINE OPTIONS
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.TP
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.B \-B
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Don't write
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.I .pyc
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files on import. See also PYTHONDONTWRITEBYTECODE.
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.TP
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.B \-b
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Issue warnings about str(bytes_instance), str(bytearray_instance)
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and comparing bytes/bytearray with str. (-bb: issue errors)
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.TP
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.BI "\-c " command
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Specify the command to execute (see next section).
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This terminates the option list (following options are passed as
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arguments to the command).
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.TP
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.BI "\-\-check-hash-based-pycs " mode
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Configure how Python evaluates the up-to-dateness of hash-based .pyc files.
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.TP
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.B \-d
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Turn on parser debugging output (for expert only, depending on
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compilation options).
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.TP
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.B \-E
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Ignore environment variables like PYTHONPATH and PYTHONHOME that modify
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the behavior of the interpreter.
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.TP
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.B \-h ", " \-? ", "\-\-help
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Prints the usage for the interpreter executable and exits.
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.TP
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.B \-i
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When a script is passed as first argument or the \fB\-c\fP option is
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used, enter interactive mode after executing the script or the
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command. It does not read the $PYTHONSTARTUP file. This can be
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useful to inspect global variables or a stack trace when a script
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raises an exception.
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.TP
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.B \-I
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Run Python in isolated mode. This also implies \fB\-E\fP and \fB\-s\fP. In
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isolated mode sys.path contains neither the script's directory nor the user's
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site-packages directory. All PYTHON* environment variables are ignored, too.
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Further restrictions may be imposed to prevent the user from injecting
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malicious code.
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.TP
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.BI "\-m " module-name
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Searches
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.I sys.path
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for the named module and runs the corresponding
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.I .py
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file as a script.
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.TP
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.B \-O
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Remove assert statements and any code conditional on the value of
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__debug__; augment the filename for compiled (bytecode) files by
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adding .opt-1 before the .pyc extension.
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.TP
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.B \-OO
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Do \fB-O\fP and also discard docstrings; change the filename for
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compiled (bytecode) files by adding .opt-2 before the .pyc extension.
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.TP
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.B \-q
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Do not print the version and copyright messages. These messages are
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also suppressed in non-interactive mode.
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.TP
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.B \-s
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Don't add user site directory to sys.path.
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.TP
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.B \-S
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Disable the import of the module
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.I site
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and the site-dependent manipulations of
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.I sys.path
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that it entails. Also disable these manipulations if
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.I site
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is explicitly imported later.
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.TP
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.B \-u
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Force the stdout and stderr streams to be unbuffered.
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This option has no effect on the stdin stream.
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.TP
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.B \-v
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Print a message each time a module is initialized, showing the place
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(filename or built-in module) from which it is loaded. When given
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twice, print a message for each file that is checked for when
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searching for a module. Also provides information on module cleanup
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at exit.
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.TP
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.B \-V ", " \-\-version
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Prints the Python version number of the executable and exits. When given
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twice, print more information about the build.
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.TP
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.BI "\-W " argument
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Warning control. Python sometimes prints warning message to
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.IR sys.stderr .
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A typical warning message has the following form:
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.IB file ":" line ": " category ": " message.
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By default, each warning is printed once for each source line where it
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occurs. This option controls how often warnings are printed.
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Multiple
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.B \-W
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options may be given; when a warning matches more than one
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option, the action for the last matching option is performed.
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Invalid
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.B \-W
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options are ignored (a warning message is printed about invalid
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options when the first warning is issued). Warnings can also be
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controlled from within a Python program using the
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.I warnings
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module.
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The simplest form of
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.I argument
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is one of the following
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.I action
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strings (or a unique abbreviation):
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.B ignore
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to ignore all warnings;
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.B default
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to explicitly request the default behavior (printing each warning once
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per source line);
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.B all
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to print a warning each time it occurs (this may generate many
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messages if a warning is triggered repeatedly for the same source
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line, such as inside a loop);
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.B module
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to print each warning only the first time it occurs in each
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module;
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.B once
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to print each warning only the first time it occurs in the program; or
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.B error
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to raise an exception instead of printing a warning message.
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The full form of
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.I argument
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is
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.IB action : message : category : module : line.
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Here,
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.I action
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is as explained above but only applies to messages that match the
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remaining fields. Empty fields match all values; trailing empty
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fields may be omitted. The
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.I message
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field matches the start of the warning message printed; this match is
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case-insensitive. The
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.I category
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field matches the warning category. This must be a class name; the
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match test whether the actual warning category of the message is a
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subclass of the specified warning category. The full class name must
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be given. The
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.I module
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field matches the (fully-qualified) module name; this match is
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case-sensitive. The
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.I line
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field matches the line number, where zero matches all line numbers and
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is thus equivalent to an omitted line number.
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.TP
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.BI "\-X " option
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Set implementation specific option. The following options are available:
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-X faulthandler: enable faulthandler
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-X showrefcount: output the total reference count and number of used
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memory blocks when the program finishes or after each statement in the
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interactive interpreter. This only works on debug builds
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-X tracemalloc: start tracing Python memory allocations using the
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tracemalloc module. By default, only the most recent frame is stored in a
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traceback of a trace. Use -X tracemalloc=NFRAME to start tracing with a
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traceback limit of NFRAME frames
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-X importtime: show how long each import takes. It shows module name,
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cumulative time (including nested imports) and self time (excluding
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nested imports). Note that its output may be broken in multi-threaded
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application. Typical usage is python3 -X importtime -c 'import asyncio'
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-X dev: enable CPython’s “development mode”, introducing additional runtime
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checks which are too expensive to be enabled by default. It will not be
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more verbose than the default if the code is correct: new warnings are
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only emitted when an issue is detected. Effect of the developer mode:
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* Add default warning filter, as -W default
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* Install debug hooks on memory allocators: see the PyMem_SetupDebugHooks() C function
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* Enable the faulthandler module to dump the Python traceback on a crash
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* Enable asyncio debug mode
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* Set the dev_mode attribute of sys.flags to True
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* io.IOBase destructor logs close() exceptions
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-X utf8: enable UTF-8 mode for operating system interfaces, overriding the default
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locale-aware mode. -X utf8=0 explicitly disables UTF-8 mode (even when it would
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otherwise activate automatically). See PYTHONUTF8 for more details
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-X pycache_prefix=PATH: enable writing .pyc files to a parallel tree rooted at the
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given directory instead of to the code tree.
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.TP
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.B \-x
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Skip the first line of the source. This is intended for a DOS
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specific hack only. Warning: the line numbers in error messages will
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be off by one!
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.SH INTERPRETER INTERFACE
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The interpreter interface resembles that of the UNIX shell: when
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called with standard input connected to a tty device, it prompts for
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||
commands and executes them until an EOF is read; when called with a
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file name argument or with a file as standard input, it reads and
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executes a
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.I script
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from that file;
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when called with
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.B \-c
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.IR command ,
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it executes the Python statement(s) given as
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.IR command .
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Here
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.I command
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may contain multiple statements separated by newlines.
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Leading whitespace is significant in Python statements!
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In non-interactive mode, the entire input is parsed before it is
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executed.
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.PP
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If available, the script name and additional arguments thereafter are
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passed to the script in the Python variable
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.IR sys.argv ,
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which is a list of strings (you must first
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.I import sys
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to be able to access it).
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If no script name is given,
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.I sys.argv[0]
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is an empty string; if
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.B \-c
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is used,
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.I sys.argv[0]
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contains the string
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.I '-c'.
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Note that options interpreted by the Python interpreter itself
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are not placed in
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.IR sys.argv .
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.PP
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In interactive mode, the primary prompt is `>>>'; the second prompt
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(which appears when a command is not complete) is `...'.
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The prompts can be changed by assignment to
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.I sys.ps1
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or
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.IR sys.ps2 .
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The interpreter quits when it reads an EOF at a prompt.
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When an unhandled exception occurs, a stack trace is printed and
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control returns to the primary prompt; in non-interactive mode, the
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interpreter exits after printing the stack trace.
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The interrupt signal raises the
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.I Keyboard\%Interrupt
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exception; other UNIX signals are not caught (except that SIGPIPE is
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sometimes ignored, in favor of the
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.I IOError
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exception). Error messages are written to stderr.
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.SH FILES AND DIRECTORIES
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These are subject to difference depending on local installation
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conventions; ${prefix} and ${exec_prefix} are installation-dependent
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and should be interpreted as for GNU software; they may be the same.
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The default for both is \fI/usr/local\fP.
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.IP \fI${exec_prefix}/bin/python\fP
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Recommended location of the interpreter.
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.PP
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.I ${prefix}/lib/python<version>
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.br
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.I ${exec_prefix}/lib/python<version>
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.RS
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Recommended locations of the directories containing the standard
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modules.
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.RE
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.PP
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.I ${prefix}/include/python<version>
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.br
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.I ${exec_prefix}/include/python<version>
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.RS
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Recommended locations of the directories containing the include files
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needed for developing Python extensions and embedding the
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interpreter.
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.RE
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.SH ENVIRONMENT VARIABLES
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.IP PYTHONHOME
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Change the location of the standard Python libraries. By default, the
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libraries are searched in ${prefix}/lib/python<version> and
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${exec_prefix}/lib/python<version>, where ${prefix} and ${exec_prefix}
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||
are installation-dependent directories, both defaulting to
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\fI/usr/local\fP. When $PYTHONHOME is set to a single directory, its value
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replaces both ${prefix} and ${exec_prefix}. To specify different values
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for these, set $PYTHONHOME to ${prefix}:${exec_prefix}.
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.IP PYTHONPATH
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Augments the default search path for module files.
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The format is the same as the shell's $PATH: one or more directory
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pathnames separated by colons.
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Non-existent directories are silently ignored.
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The default search path is installation dependent, but generally
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begins with ${prefix}/lib/python<version> (see PYTHONHOME above).
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The default search path is always appended to $PYTHONPATH.
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If a script argument is given, the directory containing the script is
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inserted in the path in front of $PYTHONPATH.
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The search path can be manipulated from within a Python program as the
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variable
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.IR sys.path .
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.IP PYTHONSTARTUP
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If this is the name of a readable file, the Python commands in that
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file are executed before the first prompt is displayed in interactive
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mode.
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The file is executed in the same name space where interactive commands
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are executed so that objects defined or imported in it can be used
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without qualification in the interactive session.
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You can also change the prompts
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.I sys.ps1
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and
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.I sys.ps2
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in this file.
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.IP PYTHONOPTIMIZE
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If this is set to a non-empty string it is equivalent to specifying
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||
the \fB\-O\fP option. If set to an integer, it is equivalent to
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||
specifying \fB\-O\fP multiple times.
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||
.IP PYTHONDEBUG
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If this is set to a non-empty string it is equivalent to specifying
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||
the \fB\-d\fP option. If set to an integer, it is equivalent to
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specifying \fB\-d\fP multiple times.
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||
.IP PYTHONDONTWRITEBYTECODE
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||
If this is set to a non-empty string it is equivalent to specifying
|
||
the \fB\-B\fP option (don't try to write
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||
.I .pyc
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||
files).
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||
.IP PYTHONINSPECT
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||
If this is set to a non-empty string it is equivalent to specifying
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||
the \fB\-i\fP option.
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||
.IP PYTHONIOENCODING
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||
If this is set before running the interpreter, it overrides the encoding used
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||
for stdin/stdout/stderr, in the syntax
|
||
.IB encodingname ":" errorhandler
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||
The
|
||
.IB errorhandler
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||
part is optional and has the same meaning as in str.encode. For stderr, the
|
||
.IB errorhandler
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||
part is ignored; the handler will always be \'backslashreplace\'.
|
||
.IP PYTHONNOUSERSITE
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||
If this is set to a non-empty string it is equivalent to specifying the
|
||
\fB\-s\fP option (Don't add the user site directory to sys.path).
|
||
.IP PYTHONUNBUFFERED
|
||
If this is set to a non-empty string it is equivalent to specifying
|
||
the \fB\-u\fP option.
|
||
.IP PYTHONVERBOSE
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||
If this is set to a non-empty string it is equivalent to specifying
|
||
the \fB\-v\fP option. If set to an integer, it is equivalent to
|
||
specifying \fB\-v\fP multiple times.
|
||
.IP PYTHONWARNINGS
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||
If this is set to a comma-separated string it is equivalent to
|
||
specifying the \fB\-W\fP option for each separate value.
|
||
.IP PYTHONHASHSEED
|
||
If this variable is set to "random", a random value is used to seed the hashes
|
||
of str and bytes 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
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||
values.
|
||
|
||
The integer must be a decimal number in the range [0,4294967295]. Specifying
|
||
the value 0 will disable hash randomization.
|
||
.IP PYTHONMALLOC
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||
Set the Python memory allocators and/or install debug hooks. The available
|
||
memory allocators are
|
||
.IR malloc
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||
and
|
||
.IR pymalloc .
|
||
The available debug hooks are
|
||
.IR debug ,
|
||
.IR malloc_debug ,
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||
and
|
||
.IR pymalloc_debug .
|
||
.IP
|
||
When Python is compiled in debug mode, the default is
|
||
.IR pymalloc_debug
|
||
and the debug hooks are automatically used. Otherwise, the default is
|
||
.IR pymalloc .
|
||
.IP PYTHONMALLOCSTATS
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||
If set to a non-empty string, Python will print statistics of the pymalloc
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||
memory allocator every time a new pymalloc object arena is created, and on
|
||
shutdown.
|
||
.IP
|
||
This variable is ignored if the
|
||
.RB $ PYTHONMALLOC
|
||
environment variable is used to force the
|
||
.BR malloc (3)
|
||
allocator of the C library, or if Python is configured without pymalloc support.
|
||
.IP PYTHONASYNCIODEBUG
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||
If this environment variable is set to a non-empty string, enable the debug
|
||
mode of the asyncio module.
|
||
.IP PYTHONTRACEMALLOC
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||
If this environment variable is set to a non-empty string, start tracing
|
||
Python memory allocations using the tracemalloc module.
|
||
.IP
|
||
The value of the variable is the maximum number of frames stored in a
|
||
traceback of a trace. For example,
|
||
.IB PYTHONTRACEMALLOC=1
|
||
stores only the most recent frame.
|
||
.IP PYTHONFAULTHANDLER
|
||
If this environment variable is set to a non-empty string,
|
||
.IR faulthandler.enable()
|
||
is called at startup: install a handler for SIGSEGV, SIGFPE, SIGABRT, SIGBUS
|
||
and SIGILL signals to dump the Python traceback.
|
||
.IP
|
||
This is equivalent to the \fB-X faulthandler\fP option.
|
||
.IP PYTHONEXECUTABLE
|
||
If this environment variable is set,
|
||
.IB sys.argv[0]
|
||
will be set to its value instead of the value got through the C runtime. Only
|
||
works on Mac OS X.
|
||
.IP PYTHONUSERBASE
|
||
Defines the user base directory, which is used to compute the path of the user
|
||
.IR site-packages
|
||
directory and Distutils installation paths for
|
||
.IR "python setup\.py install \-\-user" .
|
||
.IP 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
|
||
\fB\-X importtime\fP on the command line.
|
||
.IP 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.
|
||
.SS Debug-mode variables
|
||
Setting these variables only has an effect in a debug build of Python, that is,
|
||
if Python was configured with the
|
||
\fB\--with-pydebug\fP build option.
|
||
.IP PYTHONTHREADDEBUG
|
||
If this environment variable is set, Python will print threading debug info.
|
||
.IP PYTHONDUMPREFS
|
||
If this environment variable is set, Python will dump objects and reference
|
||
counts still alive after shutting down the interpreter.
|
||
.SH AUTHOR
|
||
The Python Software Foundation: https://www.python.org/psf/
|
||
.SH INTERNET RESOURCES
|
||
Main website: https://www.python.org/
|
||
.br
|
||
Documentation: https://docs.python.org/
|
||
.br
|
||
Developer resources: https://devguide.python.org/
|
||
.br
|
||
Downloads: https://www.python.org/downloads/
|
||
.br
|
||
Module repository: https://pypi.org/
|
||
.br
|
||
Newsgroups: comp.lang.python, comp.lang.python.announce
|
||
.SH 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.
|