Things get hairy when you want an option to take a variable number of arguments. For this case, you must write a callback, as optparse doesn't provide any built-in capabilities for it. And you have to deal with certain intricacies of conventional Unix command-line parsing that optparse normally handles for you. In particular, callbacks should implement the conventional rules for bare -- and - arguments:
If you want an option that takes a variable number of arguments, there are several subtle, tricky issues to worry about. The exact implementation you choose will be based on which trade-offs you're willing to make for your application (which is why optparse doesn't support this sort of thing directly).
Nevertheless, here's a stab at a callback for an option with variable arguments:
def vararg_callback(option, opt_str, value, parser): assert value is None done = 0 value =  rargs = parser.rargs while rargs: arg = rargs # Stop if we hit an arg like "--foo", "-a", "-fx", "--file=f", # etc. Note that this also stops on "-3" or "-3.0", so if # your option takes numeric values, you will need to handle # this. if ((arg[:2] == "--" and len(arg) > 2) or (arg[:1] == "-" and len(arg) > 1 and arg != "-")): break else: value.append(arg) del rargs setattr(parser.values, option.dest, value) [...] parser.add_option("-c", "--callback", action="callback", callback=varargs)
The main weakness with this particular implementation is that negative
numbers in the arguments following
"-c" will be interpreted as
further options (probably causing an error), rather than as arguments to
"-c". Fixing this is left as an exercise for the reader.
See About this document... for information on suggesting changes.