Expert Python Programming - Third Edition

Using *args and **kwargs magic arguments carefully

The *args and **kwargs arguments can break the robustness of a function or method. They make the signature fuzzy, and the code often starts to become a small argument parser where it should not, for example:

def fuzzy_thing(**kwargs):    if 'do_this' in kwargs:        print('ok i did this')    if 'do_that' in kwargs:        print('that is done')    print('ok')>>> fuzzy_thing(do_this=1)ok i did thisok>>> fuzzy_thing(do_that=1)that is doneok>>> fuzzy_thing(what_about_that=1)ok

If the argument list gets long and complex, it is tempting to add magic arguments. But this is more a sign of a weak function or method that should be broken into pieces or refactored.

When *args is used to deal with a sequence of elements ...