On Wed, Oct 22, 2014 at 12:44 PM, Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > def do_something(instance_or_id): > instance = Model.get(instance_or_id) > assert isinstance(instance, Model) > # Code that assumes that instance is an object of type Model > > > That means that the logic for what is acceptable as a Model is all in one > place, namely the Model.get method, and callers don't need to care about > the pre-condition "argument is a Model or an integer ID", they only need to > care about the post-condition "result of get() is a Model".
And at that point, the assertion is redundant, on par with: a = len(seq) assert isinstance(a, int) because you shouldn't have to assert what's part of a function's guarantee. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
