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143 lines
5.5 KiB
ReStructuredText
143 lines
5.5 KiB
ReStructuredText
:mod:`getopt` --- Parser for command line options
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=================================================
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.. module:: getopt
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:synopsis: Portable parser for command line options; support both short and
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long option names.
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This module helps scripts to parse the command line arguments in ``sys.argv``.
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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.
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A more convenient, flexible, and powerful alternative is the
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:mod:`optparse` module.
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This module provides two functions and an
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exception:
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.. function:: getopt(args, shortopts, longopts=[])
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Parses command line options and parameter list. *args* is the argument list to
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be parsed, without the leading reference to the running program. Typically, this
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means ``sys.argv[1:]``. *shortopts* is the string of option letters that the
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script wants to recognize, with options that require an argument followed by a
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colon (``':'``; i.e., the same format that Unix :cfunc:`getopt` uses).
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.. note::
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Unlike GNU :cfunc:`getopt`, after a non-option argument, all further
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arguments are considered also non-options. This is similar to the way
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non-GNU Unix systems work.
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*longopts*, if specified, must be a list of strings with the names of the
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long options which should be supported. The leading ``'--'`` characters
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should not be included in the option name. Long options which require an
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argument should be followed by an equal sign (``'='``). To accept only long
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options, *shortopts* should be an empty string. Long options on the command line
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can be recognized so long as they provide a prefix of the option name that
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matches exactly one of the accepted options. For example, if *longopts* is
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``['foo', 'frob']``, the option :option:`--fo` will match as :option:`--foo`,
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but :option:`--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,
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value)`` pairs; the second is the list of program arguments left after the
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option list was stripped (this is a trailing slice of *args*). Each
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option-and-value pair returned has the option as its first element, prefixed
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with a hyphen for short options (e.g., ``'-x'``) or two hyphens for long
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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
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options occur in the list in the same order in which they were found, thus
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allowing multiple occurrences. Long and short options may be mixed.
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.. function:: gnu_getopt(args, shortopts, longopts=[])
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This function works like :func:`getopt`, except that GNU style scanning mode is
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used by default. This means that option and non-option arguments may be
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intermixed. The :func:`getopt` function stops processing options as soon as a
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non-option argument is encountered.
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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
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soon as a non-option argument is encountered.
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.. exception:: GetoptError
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This is raised when an unrecognized option is found in the argument list or when
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an option requiring an argument is given none. The argument to the exception is
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a string indicating the cause of the error. For long options, an argument given
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to an option which does not require one will also cause this exception to be
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raised. The attributes :attr:`msg` and :attr:`opt` give the error message and
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related option; if there is no specific option to which the exception relates,
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:attr:`opt` is an empty string.
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.. XXX deprecated?
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.. exception:: error
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Alias for :exc:`GetoptError`; for backward compatibility.
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An example using only Unix style options:
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>>> import getopt
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>>> args = '-a -b -cfoo -d bar a1 a2'.split()
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>>> args
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['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2']
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>>> optlist, args = getopt.getopt(args, 'abc:d:')
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>>> optlist
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[('-a', ''), ('-b', ''), ('-c', 'foo'), ('-d', 'bar')]
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>>> args
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['a1', 'a2']
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Using long option names is equally easy:
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>>> s = '--condition=foo --testing --output-file abc.def -x a1 a2'
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>>> args = s.split()
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>>> args
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['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2']
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>>> optlist, args = getopt.getopt(args, 'x', [
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... 'condition=', 'output-file=', 'testing'])
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>>> optlist
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[('--condition', 'foo'), ('--testing', ''), ('--output-file', 'abc.def'), ('-x', '')]
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>>> args
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['a1', 'a2']
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In a script, typical usage is something like this::
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import getopt, sys
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def main():
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try:
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opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
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except getopt.GetoptError as err:
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# print help information and exit:
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print(err) # will print something like "option -a not recognized"
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usage()
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sys.exit(2)
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output = None
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verbose = False
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for o, a in opts:
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if o == "-v":
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verbose = True
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elif o in ("-h", "--help"):
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usage()
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sys.exit()
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elif o in ("-o", "--output"):
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output = a
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else:
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assert False, "unhandled option"
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# ...
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if __name__ == "__main__":
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main()
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.. seealso::
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Module :mod:`optparse`
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More object-oriented command line option parsing.
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