Callbacks are functions called when an optparse.OptionParser() object has a callback option defined (don't know how to say this less obvious sounding...) (they are documented in http://docs.python.org/lib/optparse-option-callbacks.html)
Example (based on an example in the documentation): this script: -#!/usr/bin/env python -import optparse -def record_foo_seen(option, opt_str, value, parser): - print 'saw foo' - -parser = optparse.OptionParser() -parser.add_option("--foo", action="callback", callback=record_foo_seen) -(options, args) = parser.parse_args() - -print options, args prints when executed with or without argument: [EMAIL PROTECTED]:~$ ./test2.py --foo saw foo {} [] [EMAIL PROTECTED]:~$ ./test2.py {} [] [EMAIL PROTECTED]:~$ -- http://mail.python.org/mailman/listinfo/python-list