Python Library Reference

6.21.4.8 Callback example 5: fixed arguments

Things get slightly more interesting when you define callback options that take a fixed number of arguments. Specifying that a callback option takes arguments is similar to defining a store or append option: if you define type, then the option takes one argument that must be convertible to that type; if you further define nargs, then the option takes nargs arguments.

Here's an example that just emulates the standard store action:

def store_value(option, opt_str, value, parser):
    setattr(parser.values, option.dest, value)
[...]
parser.add_option("--foo",
                  action="callback", callback=store_value,
                  type="int", nargs=3, dest="foo")

Note that optparse takes care of consuming 3 arguments and converting them to integers for you; all you have to do is store them. (Or whatever; obviously you don't need a callback for this example.)

Python Library Reference

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Release 2.4c1, documentation updated on 18 November 2004.