cpython/Doc/library/getopt.rst

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:mod:`getopt` --- C-style parser for command line options
=========================================================
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.. module:: getopt
:synopsis: Portable parser for command line options; support both short and long option
names.
.. note::
The :mod:`getopt` module is a parser for command line options whose API is
designed to be familiar to users of the C :cfunc:`getopt` function. Users who
are unfamiliar with the C :cfunc:`getopt` function or who would like to write
less code and get better help and error messages should consider using the
:mod:`argparse` module instead.
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This module helps scripts to parse the command line arguments in ``sys.argv``.
It supports the same conventions as the Unix :cfunc:`getopt` function (including
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the special meanings of arguments of the form '``-``' and '``--``'). Long
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options similar to those supported by GNU software may be used as well via an
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optional third argument.
A more convenient, flexible, and powerful alternative is the
:mod:`optparse` module.
This module provides two functions and an
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exception:
.. function:: getopt(args, options[, long_options])
Parses command line options and parameter list. *args* is the argument list to
be parsed, without the leading reference to the running program. Typically, this
means ``sys.argv[1:]``. *options* is the string of option letters that the
script wants to recognize, with options that require an argument followed by a
colon (``':'``; i.e., the same format that Unix :cfunc:`getopt` uses).
.. note::
Unlike GNU :cfunc:`getopt`, after a non-option argument, all further
arguments are considered also non-options. This is similar to the way
non-GNU Unix systems work.
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*long_options*, if specified, must be a list of strings with the names of the
Merged revisions 86521,86632,86823-86824,87294,87296,87300,87302 via svnmerge from svn+ssh://pythondev@svn.python.org/python/branches/py3k ........ r86521 | eric.araujo | 2010-11-18 17:38:46 +0100 (jeu., 18 nov. 2010) | 17 lines Fix usage of :option: in the docs (#9312). :option: is used to create a link to an option of python, not to mark up any instance of any arbitrary command-line option. These were changed to ````. For modules which do have a command-line interface, lists of options have been properly marked up with the program/cmdoption directives combo. Options defined in such blocks can be linked to with :option: later in the same file, they won’t link to an option of python. Finally, the markup of command-line fragments in optparse.rst has been cleaned to use ``x`` instead of ``"x"``, keeping that latter form for actual Python strings. Patch by Eli Bendersky and Éric Araujo. ........ r86632 | eric.araujo | 2010-11-21 04:09:17 +0100 (dim., 21 nov. 2010) | 2 lines Style edits in followup to r86521 (#9312) ........ r86823 | eric.araujo | 2010-11-27 00:31:07 +0100 (sam., 27 nov. 2010) | 2 lines Use link-generating markup (see #9312) ........ r86824 | eric.araujo | 2010-11-27 00:46:18 +0100 (sam., 27 nov. 2010) | 2 lines Rewrap long lines + minor edits ........ r87294 | eric.araujo | 2010-12-16 01:07:01 +0100 (jeu., 16 déc. 2010) | 2 lines No need to generate a link for something that’s just above. ........ r87296 | eric.araujo | 2010-12-16 01:23:30 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m” instead of direct filename. ........ r87300 | eric.araujo | 2010-12-16 02:40:26 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m test” over test.regrtest (r87296 followup) ........ r87302 | eric.araujo | 2010-12-16 03:10:11 +0100 (jeu., 16 déc. 2010) | 2 lines Add versionadded directive missing from r78983. ........
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long options which should be supported. The leading ``'--'``
characters should not be included in the option name. Long options which
require an argument should be followed by an equal sign (``'='``). Optional
arguments are not supported. To accept only long options, *options* should
be an empty string. Long options on the command line can be recognized so
long as they provide a prefix of the option name that matches exactly one of
the accepted options. For example, if *long_options* is ``['foo', 'frob']``,
Merged revisions 86521,86632,86823-86824,87294,87296,87300,87302 via svnmerge from svn+ssh://pythondev@svn.python.org/python/branches/py3k ........ r86521 | eric.araujo | 2010-11-18 17:38:46 +0100 (jeu., 18 nov. 2010) | 17 lines Fix usage of :option: in the docs (#9312). :option: is used to create a link to an option of python, not to mark up any instance of any arbitrary command-line option. These were changed to ````. For modules which do have a command-line interface, lists of options have been properly marked up with the program/cmdoption directives combo. Options defined in such blocks can be linked to with :option: later in the same file, they won’t link to an option of python. Finally, the markup of command-line fragments in optparse.rst has been cleaned to use ``x`` instead of ``"x"``, keeping that latter form for actual Python strings. Patch by Eli Bendersky and Éric Araujo. ........ r86632 | eric.araujo | 2010-11-21 04:09:17 +0100 (dim., 21 nov. 2010) | 2 lines Style edits in followup to r86521 (#9312) ........ r86823 | eric.araujo | 2010-11-27 00:31:07 +0100 (sam., 27 nov. 2010) | 2 lines Use link-generating markup (see #9312) ........ r86824 | eric.araujo | 2010-11-27 00:46:18 +0100 (sam., 27 nov. 2010) | 2 lines Rewrap long lines + minor edits ........ r87294 | eric.araujo | 2010-12-16 01:07:01 +0100 (jeu., 16 déc. 2010) | 2 lines No need to generate a link for something that’s just above. ........ r87296 | eric.araujo | 2010-12-16 01:23:30 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m” instead of direct filename. ........ r87300 | eric.araujo | 2010-12-16 02:40:26 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m test” over test.regrtest (r87296 followup) ........ r87302 | eric.araujo | 2010-12-16 03:10:11 +0100 (jeu., 16 déc. 2010) | 2 lines Add versionadded directive missing from r78983. ........
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the option ``--fo`` will match as ``--foo``, but ``--f``
will not match uniquely, so :exc:`GetoptError` will be raised.
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The return value consists of two elements: the first is a list of ``(option,
value)`` pairs; the second is the list of program arguments left after the
option list was stripped (this is a trailing slice of *args*). Each
option-and-value pair returned has the option as its first element, prefixed
with a hyphen for short options (e.g., ``'-x'``) or two hyphens for long
Merged revisions 86521,86632,86823-86824,87294,87296,87300,87302 via svnmerge from svn+ssh://pythondev@svn.python.org/python/branches/py3k ........ r86521 | eric.araujo | 2010-11-18 17:38:46 +0100 (jeu., 18 nov. 2010) | 17 lines Fix usage of :option: in the docs (#9312). :option: is used to create a link to an option of python, not to mark up any instance of any arbitrary command-line option. These were changed to ````. For modules which do have a command-line interface, lists of options have been properly marked up with the program/cmdoption directives combo. Options defined in such blocks can be linked to with :option: later in the same file, they won’t link to an option of python. Finally, the markup of command-line fragments in optparse.rst has been cleaned to use ``x`` instead of ``"x"``, keeping that latter form for actual Python strings. Patch by Eli Bendersky and Éric Araujo. ........ r86632 | eric.araujo | 2010-11-21 04:09:17 +0100 (dim., 21 nov. 2010) | 2 lines Style edits in followup to r86521 (#9312) ........ r86823 | eric.araujo | 2010-11-27 00:31:07 +0100 (sam., 27 nov. 2010) | 2 lines Use link-generating markup (see #9312) ........ r86824 | eric.araujo | 2010-11-27 00:46:18 +0100 (sam., 27 nov. 2010) | 2 lines Rewrap long lines + minor edits ........ r87294 | eric.araujo | 2010-12-16 01:07:01 +0100 (jeu., 16 déc. 2010) | 2 lines No need to generate a link for something that’s just above. ........ r87296 | eric.araujo | 2010-12-16 01:23:30 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m” instead of direct filename. ........ r87300 | eric.araujo | 2010-12-16 02:40:26 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m test” over test.regrtest (r87296 followup) ........ r87302 | eric.araujo | 2010-12-16 03:10:11 +0100 (jeu., 16 déc. 2010) | 2 lines Add versionadded directive missing from r78983. ........
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options (e.g., ``'--long-option'``), and the option argument as its
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second element, or an empty string if the option has no argument. The
options occur in the list in the same order in which they were found, thus
allowing multiple occurrences. Long and short options may be mixed.
.. function:: gnu_getopt(args, options[, long_options])
This function works like :func:`getopt`, except that GNU style scanning mode is
used by default. This means that option and non-option arguments may be
intermixed. The :func:`getopt` function stops processing options as soon as a
non-option argument is encountered.
Merged revisions 86521,86632,86823-86824,87294,87296,87300,87302 via svnmerge from svn+ssh://pythondev@svn.python.org/python/branches/py3k ........ r86521 | eric.araujo | 2010-11-18 17:38:46 +0100 (jeu., 18 nov. 2010) | 17 lines Fix usage of :option: in the docs (#9312). :option: is used to create a link to an option of python, not to mark up any instance of any arbitrary command-line option. These were changed to ````. For modules which do have a command-line interface, lists of options have been properly marked up with the program/cmdoption directives combo. Options defined in such blocks can be linked to with :option: later in the same file, they won’t link to an option of python. Finally, the markup of command-line fragments in optparse.rst has been cleaned to use ``x`` instead of ``"x"``, keeping that latter form for actual Python strings. Patch by Eli Bendersky and Éric Araujo. ........ r86632 | eric.araujo | 2010-11-21 04:09:17 +0100 (dim., 21 nov. 2010) | 2 lines Style edits in followup to r86521 (#9312) ........ r86823 | eric.araujo | 2010-11-27 00:31:07 +0100 (sam., 27 nov. 2010) | 2 lines Use link-generating markup (see #9312) ........ r86824 | eric.araujo | 2010-11-27 00:46:18 +0100 (sam., 27 nov. 2010) | 2 lines Rewrap long lines + minor edits ........ r87294 | eric.araujo | 2010-12-16 01:07:01 +0100 (jeu., 16 déc. 2010) | 2 lines No need to generate a link for something that’s just above. ........ r87296 | eric.araujo | 2010-12-16 01:23:30 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m” instead of direct filename. ........ r87300 | eric.araujo | 2010-12-16 02:40:26 +0100 (jeu., 16 déc. 2010) | 2 lines Advertise “python -m test” over test.regrtest (r87296 followup) ........ r87302 | eric.araujo | 2010-12-16 03:10:11 +0100 (jeu., 16 déc. 2010) | 2 lines Add versionadded directive missing from r78983. ........
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If the first character of the option string is ``'+'``, or if the environment
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variable :envvar:`POSIXLY_CORRECT` is set, then option processing stops as
soon as a non-option argument is encountered.
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.. versionadded:: 2.3
.. exception:: GetoptError
This is raised when an unrecognized option is found in the argument list or when
an option requiring an argument is given none. The argument to the exception is
a string indicating the cause of the error. For long options, an argument given
to an option which does not require one will also cause this exception to be
raised. The attributes :attr:`msg` and :attr:`opt` give the error message and
related option; if there is no specific option to which the exception relates,
:attr:`opt` is an empty string.
.. versionchanged:: 1.6
Introduced :exc:`GetoptError` as a synonym for :exc:`error`.
.. exception:: error
Alias for :exc:`GetoptError`; for backward compatibility.
An example using only Unix style options:
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>>> import getopt
>>> args = '-a -b -cfoo -d bar a1 a2'.split()
>>> args
['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'abc:d:')
>>> optlist
[('-a', ''), ('-b', ''), ('-c', 'foo'), ('-d', 'bar')]
>>> args
['a1', 'a2']
Using long option names is equally easy:
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>>> s = '--condition=foo --testing --output-file abc.def -x a1 a2'
>>> args = s.split()
>>> args
['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'x', [
... 'condition=', 'output-file=', 'testing'])
>>> optlist
[('--condition', 'foo'), ('--testing', ''), ('--output-file', 'abc.def'), ('-x', '')]
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>>> args
['a1', 'a2']
In a script, typical usage is something like this::
import getopt, sys
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def main():
try:
opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
except getopt.GetoptError, err:
# print help information and exit:
print str(err) # will print something like "option -a not recognized"
usage()
sys.exit(2)
output = None
verbose = False
for o, a in opts:
if o == "-v":
verbose = True
elif o in ("-h", "--help"):
usage()
sys.exit()
elif o in ("-o", "--output"):
output = a
else:
assert False, "unhandled option"
# ...
if __name__ == "__main__":
main()
Note that an equivalent command line interface could be produced with less code
and more informative help and error messages by using the :mod:`argparse` module::
import argparse
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('-o', '--output')
parser.add_argument('-v', dest='verbose', action='store_true')
args = parser.parse_args()
# ... do something with args.output ...
# ... do something with args.verbose ..
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.. seealso::
Module :mod:`argparse`
Alternative command line option and argument parsing library.
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