cpython/Lib/getopt.py

# module getopt -- Standard command line processing.

# Function getopt.getopt() has a different interface but provides the
# similar functionality to the Unix getopt() function, with the
# addition of long-option support.  (Long option support added by Lars
# Wirzenius <liw@iki.fi>.)

# It has two required arguments: the first should be argv[1:] (it
# doesn't want the script name), the second the string of option
# letters as passed to Unix getopt() (i.e., a string of allowable
# option letters, with options requiring an argument followed by a
# colon).

# The optional third argument, if present, getopt.getopt works similar
# to the GNU getopt_long function (but optional arguments are not
# supported).  The third argument should be a list of strings that
# name the long options.  If the name ends '=', the argument requires
# an argument.

# It raises the exception getopt.error with a string argument if it
# detects an error.

# It returns two values:
# (1)   a list of pairs (option, option_argument) giving the options in
#       the order in which they were specified.  (I'd use a dictionary
#       but applications may depend on option order or multiple
#       occurrences.)  Boolean options have '' as option_argument.
# (2)   the list of remaining arguments (may be empty).

import string

error = 'getopt.error'

def getopt(args, shortopts, longopts = []):
    list = []
    longopts = longopts[:]
    longopts.sort()
    while args and args[0][:1] == '-' and args[0] != '-':
        if args[0] == '--':
            args = args[1:]
            break
        if args[0][:2] == '--':
            list, args = do_longs(list, args[0][2:], longopts, args[1:])
        else:
            list, args = do_shorts(list, args[0][1:], shortopts, args[1:])

    return list, args

def do_longs(list, opt, longopts, args):
    try:
        i = string.index(opt, '=')
        opt, optarg = opt[:i], opt[i+1:]
    except ValueError:
        optarg = None

    has_arg, opt = long_has_args(opt, longopts)
    if has_arg:
        if optarg is None:
            if not args:
                raise error, 'option --%s requires argument' % opt
            optarg, args = args[0], args[1:]
    elif optarg:
        raise error, 'option --%s must not have an argument' % opt
    list.append(('--' + opt, optarg or ''))
    return list, args

# Return:
#   has_arg?
#   full option name
def long_has_args(opt, longopts):
    optlen = len(opt)
    for i in range(len(longopts)):
        x, y = longopts[i][:optlen], longopts[i][optlen:]
        if opt != x:
            continue
        if y != '' and y != '=' and i+1 < len(longopts):
            if opt == longopts[i+1][:optlen]:
                raise error, 'option --%s not a unique prefix' % opt
        if longopts[i][-1:] in ('=', ):
            return 1, longopts[i][:-1]
        return 0, longopts[i]
    raise error, 'option --' + opt + ' not recognized'

def do_shorts(list, optstring, shortopts, args):
    while optstring != '':
        opt, optstring = optstring[0], optstring[1:]
        if short_has_arg(opt, shortopts):
            if optstring == '':
                if not args:
                    raise error, 'option -%s requires argument' % opt
                optstring, args = args[0], args[1:]
            optarg, optstring = optstring, ''
        else:
            optarg = ''
        list.append(('-' + opt, optarg))
    return list, args

def short_has_arg(opt, shortopts):
    for i in range(len(shortopts)):
        if opt == shortopts[i] != ':':
            return shortopts[i+1:i+2] == ':'
    raise error, 'option -%s not recognized' % opt

if __name__ == '__main__':
    import sys
    print getopt(sys.argv[1:], "a:b", ["alpha=", "beta"])