problem with optparse

[Neal Becker]

This example is right out of python library reference.  What's wrong here?

import optparse

def store_value(option, opt_str, value, parser):
    setattr(parser.values, option.dest, value)

parser = optparse.OptionParser()
parser.add_option("--foo",
                  action="callback", callback=store_value,
                  type="int", nargs=3, dest="foo")

(opt,args) = parser.parse_args ('--foo a b c'.split())

[...]
/usr/lib64/python2.5/optparse.pyc in _process_args(self, largs, rargs, values)
   1423             elif self.allow_interspersed_args:
   1424                 largs.append(arg)
-> 1425                 del rargs[0]
   1426             else:
   1427                 return                  # stop now, leave this arg in rargs

TypeError: 'str' object doesn't support item deletion