Missing __length_hint__ in __getitem__ iterator

[Giovanni Bajo]

Hello,

given the following 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:
['__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?

 

[Peter Otten]

Hello,

given the following 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:
['__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:
.... def __getitem__(self, index): return index
.... def __len__(self): return 42
....42

Peter

 

[Giovanni Bajo]

It's there, just not doctored into the dir() output:

... def __getitem__(self, index): return index
... def __len__(self): return 42
...
42

Peter

Ah well, actually it's there also in dir(), you just need to use Python 2.5
of course