Hello,
Well, I guess this isn't a bug (its only a hint) - but IronPython
doesn't use length hint. :-)
CPython
>>> class X(object):
... def __iter__(self):
... return iter([1,2,3])
... def __length_hint__(self):
... print 'length hint'
... return 3
...
>>> x = X()
>>> list(x)
length hint
[1, 2, 3]
IronPython
>>> class X(object):
... def __iter__(self):
... return iter([1,2,3])
... def __length_hint__(self):
... print 'length hint'
... return 3
...
>>> x = X()
>>> list(x)
[1, 2, 3]
>>>
CPython uses it as an optimisation to preallocate space for the list.
You can bet somebody, somewhere is writing code that depends on length
hint being called... Actually probably not, but it's one of those
methods like '__reversed__' and '__missing__' that I've only recently
discovered. I was impressed that IronPython supported '__missing__' by
the way.
Michael
--
http://www.ironpythoninaction.com/
http://www.voidspace.org.uk/blog
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