Antoon Pardon <antoon.par...@rece.vub.ac.be>: > Op 23-06-16 om 11:10 schreef Marko Rauhamaa: >> The __len__ method is not guaranteed to execute in O(1). See: >> >> <URL: https://docs.python.org/3/reference/datamodel.html?highlig >> ht=__len__#object.__len__> > > As far as I can see, neither is the __bool__ method.
Correct, but in the absence of an __empty__ method, __bool__ gives the class the best opportunity to check for emptiness quickly. This is not only a theoretical concern. It's quite common for data structures not to maintain an element count because it's extra baggage that's not always needed and any application could keep a track of. However, an emptiness check is often trivial. Marko -- https://mail.python.org/mailman/listinfo/python-list
