I have optparse code that parses a command line containing intermixed positional and optional arguments, where the optional arguments set the context for the following positional arguments. For example,
myprogram.py arg1 -c33 arg2 arg3 -c44 arg4 'arg1' is processed in a default context, 'args2' and 'arg3' in context '33', and 'arg4' in context '44'. I am trying to do the same using argparse but it appears to be not doable in a documented way. Here is the working optparse code (which took 30 minutes to write using just the optparse docs): import optparse def append_with_pos (option, opt_str, value, parser): if getattr (parser.values, option.dest, None) is None: setattr (parser.values, option.dest, []) getattr (parser.values, option.dest).append ((value, len (parser.largs))) def opt_parse(): p = optparse.OptionParser() p.add_option ("-c", type=int, action='callback', callback=append_with_pos) opts, args = p.parse_args() return args, opts if __name__ == '__main__': args, opts = opt_parse() print args, opts Output from the command line above: ['arg1', 'arg2', 'arg3', 'arg4'] {'c': [(33, 1), (44, 3)]} The -c values are stored as (value, arglist_position) tuples. Here is an attempt to convert to argparse using the guidelines in the argparse docs: import argparse class AppendWithPos (argparse.Action): def __call__ (self, parser, namespace, values, option_string=None): if getattr (namespace, self.dest, None) is None: setattr (namespace, self.dest, []) getattr (namespace, self.dest).extend ((values, len (parser.largs))) def arg_parse(): p = argparse.ArgumentParser (description='description') p.add_argument ('src', nargs='*') p.add_argument ('-c', type=int, action=AppendWithPos) opts = p.parse_args() return opts if __name__ == '__main__': opts = arg_parse() print opts This fails with, AttributeError: 'ArgumentParser' object has no attribute 'largs' and of course, the argparse.parser is not documented beyond how to instantiate it. Even were that not a problem, argparse complains about "unrecognised arguments" for any positional arguments that occur after an optional one. I've been farting with this code for a day now. Any suggestions on how I can convince argparse to do what optparse does easily will be very welcome. (I tried parse_known_args() but that breaks help and requires me to detect truly unknown arguments.) (Python 2.7.1 if it matters and apologies if Google mangles the formatting of this post.) -- http://mail.python.org/mailman/listinfo/python-list