Giovanni Bajo wrote: > Hello, > > given the following object: > > >>> class A(object): > ... def __getitem__(self, idx): > ... if idx >= 10: raise IndexError > ... return idx > ... def __len__(self): > ... return 10 > ... > > I noticed that the iterator that Python constructs: > > >>> a = A() > >>> i = iter(a) > >>> dir(i) > ['__class__', '__delattr__', '__doc__', '__getattribute__', '__hash__', > '__init__', '__iter__', '__len__', '__new__', '__reduce__', > '__reduce_ex__', '__repr__', '__setattr__', '__str__', 'next'] > > does not have a __length_hint__ method. > > Is this just a missing optimization, or there is a deep semantic reason > for which a __length_hint__ could not be constructed out of the __len__ > result?
It's there, just not doctored into the dir() output: >>> class A(object): ... def __getitem__(self, index): return index ... def __len__(self): return 42 ... >>> iter(A()).__length_hint__ <built-in method __length_hint__ of iterator object at 0x401d558c> >>> iter(A()).__length_hint__() 42 Peter -- http://mail.python.org/mailman/listinfo/python-list
