Antoon Pardon writes: > Op 23-06-16 om 12:59 schreef Marko Rauhamaa: >> Antoon Pardon <antoon.par...@rece.vub.ac.be>: >> >>> Op 23-06-16 om 11:53 schreef Marko Rauhamaa: >>> Maybe something like this: >>> >>> def empty(sq): >>> try: >>> iter(sq).next() >>> except StopIteration: >>> return False >>> except: >>> raise TypeError >>> else: >>> return True >> That may or may not be as effective as a boolean check. The point is, >> Python has already declared that __bool__ is the canonical emptiness >> checker. You could even say that it's the principal purpose of the >> __bool__ method. > > I think it is wrong to say __bool__ is the canonical emptiness checker. > It can be used for anything where you somehow think it is reasonable > to make a distinction between truthy and falsy. Even when talking > about emptyness doesn't make sense. > > The function above at least raises an exception in a lot of cases > where the class provides booly behaviour yet emptyness wouldn't make > sense.
It also *changes* many things where emptiness *would* make sense. In particular, it can first *make* a thing empty and then happily declare it not empty. Not good. Is "sq" mnemonic for something? -- https://mail.python.org/mailman/listinfo/python-list
