On Fri, 29 Jul 2016, 09:20 Steven D'Aprano, <st...@pearwood.info> wrote:
> I'm not sure that partial is intended as an optimization. It may end up > saving time by avoiding evaluating arguments, but that's not why it exists. > It exists to enable the functional programming idiom of partial evaluation > in a simpler, more idiomatic (for functional programmers) way: > > function_of_one_argument = function_of_two_arguments(arg) > > rather than: > > def function_of_one_argument(x): > return function_of_two_arguments(arg, x) > I also find it useful for passing pre-argumented functions as callbacks or similar, e.g. as finalizers in pytest or cleanup in Unit test. Those mechanisms want a callable with no arguments: `request.addfinalizer(functools.partial(cleanup(a, few, inputs)))` And the partial is quite happy to execute later with no (new) arguments. (in general I prefer to use @pytest.yield_fixture but that doesn't always fit) > -- https://mail.python.org/mailman/listinfo/python-list
