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"""Parser for command line options.

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() -- Parse command line options

GetoptError -- exception (class) raised with 'opt' attribute, which is the

option involved with the exception.

"""

# Long option support added by Lars Wirzenius <liw@iki.fi>.

# Gerrit Holl <gerrit@nl.linux.org> moved the string-based exceptions

# to class-based exceptions.

__all__ = ["GetoptError","error","getopt"]

class GetoptError(Exception):

    opt = ''

    msg = ''

    def __init__(self, msg, opt):

        self.msg = msg

        self.opt = opt

        Exception.__init__(self, msg, opt)

    def __str__(self):

        return self.msg

error = GetoptError # backward compatibility

def getopt(args, shortopts, longopts = []):

    """getopt(args, options[, long_options]) -> opts, args

    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:]".  shortopts

    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).  If

    specified, longopts is 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.  Options

    which require an argument should be followed by an equal sign

    ('=').

    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 the first argument).  Each option-and-value pair returned has

    the option as its first element, prefixed with a hyphen (e.g.,

    '-x'), 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.

    """

    opts = []

    if type(longopts) == type(""):

        longopts = [longopts]

    else:

        longopts = list(longopts)

    while args and args[0].startswith('-') and args[0] != '-':

        if args[0] == '--':

            args = args[1:]

            break

        if args[0][:2] == '--':

            opts, args = do_longs(opts, args[0][2:], longopts, args[1:])

        else:

            opts, args = do_shorts(opts, args[0][1:], shortopts, args[1:])

    return opts, args

def do_longs(opts, opt, longopts, args):

    try:

        i = opt.index('=')

    except ValueError:

        optarg = None

    else:

        opt, optarg = opt[:i], opt[i+1:]

    has_arg, opt = long_has_args(opt, longopts)

    if has_arg:

        if optarg is None:

            if not args:

                raise GetoptError('option --%s requires argument' % opt, opt)

            optarg, args = args[0], args[1:]

    elif optarg:

        raise GetoptError('option --%s must not have an argument' % opt, opt)

    opts.append(('--' + opt, optarg or ''))

    return opts, args

# Return:

#   has_arg?

#   full option name

def long_has_args(opt, longopts):

    possibilities = [o for o in longopts if o.startswith(opt)]

    if not possibilities:

        raise GetoptError('option --%s not recognized' % opt, opt)

    # Is there an exact match?

    if opt in possibilities:

        return 0, opt

    elif opt + '=' in possibilities:

        return 1, opt

    # No exact match, so better be unique.

    if len(possibilities) > 1:

        # XXX since possibilities contains all valid continuations, might be

        # nice to work them into the error msg

        raise GetoptError('option --%s not a unique prefix' % opt, opt)

    assert len(possibilities) == 1

    unique_match = possibilities[0]

    has_arg = unique_match.endswith('=')

    if has_arg:

        unique_match = unique_match[:-1]

    return has_arg, unique_match

def do_shorts(opts, optstring, shortopts, args):

    while optstring != '':

        opt, optstring = optstring[0], optstring[1:]

        if short_has_arg(opt, shortopts):

            if optstring == '':

                if not args:

                    raise GetoptError('option -%s requires argument' % opt, opt)

                optstring, args = args[0], args[1:]

            optarg, optstring = optstring, ''

        else:

            optarg = ''

        opts.append(('-' + opt, optarg))

    return opts, args

def short_has_arg(opt, shortopts):

    for i in range(len(shortopts)):

        if opt == shortopts[i] != ':':

            return shortopts[i+1:i+2] == ':'

    raise GetoptError('option -%s not recognized' % opt, opt)

if __name__ == '__main__':

    import sys

    print getopt(sys.argv[1:], "a:b", ["alpha=", "beta"])