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(python2.1-lib.info)getopt

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Parser for command line options
===============================

Portable parser for command line options; support both short and long
option names.

This module helps scripts to parse the command line arguments in
`sys.argv'.  It supports the same conventions as the UNIX `getopt()'
function (including the special meanings of arguments of the form ``-''
and ``-'`-'').  Long options similar to those supported by GNU software
may be used as well via an optional third argument.  This module
provides a single function and an exception:

`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 `getopt()' uses).

     *Note:* Unlike GNU `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.

     LONG_OPTIONS, if specified, must be a list of strings with the
     names of the 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 (`=').  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, it
     LONG_OPTIONS is `['foo', 'frob']', the option `--fo' will match as
     `--foo', but `--f' will not match uniquely, so `GetoptError' will
     be raised.

     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 options (e.g.,
     `'-'`-long-option''), and the option argument as its 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.

`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 `msg' and `opt' give the error message and related
     option; if there is no specific option to which the exception
     relates, `opt' is an empty string.

     _Changed in Python version 1.6_

`error'
     Alias for `GetoptError'; for backward compatibility.

An example using only UNIX style options:

     >>> 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:

     >>> 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',
      '')]
     >>> args
     ['a1', 'a2']

In a script, typical usage is something like this:

     import getopt, sys
     
     def main():
         try:
             opts, args = getopt.getopt(sys.argv[1:], "ho:", ["help", "output="])
         except getopt.GetoptError:
             # print help information and exit:
             usage()
             sys.exit(2)
         output = None
         for o, a in opts:
             if o in ("-h", "--help"):
                 usage()
                 sys.exit()
             if o in ("-o", "--output"):
                 output = a
         # ...
     
     if __name__ == "__main__":
         main()


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