On Tue, Jul 17, 2012 at 1:03 PM, Alex Gaynor <alex.gay...@gmail.com> wrote: > I've updated the PEP to reflect the discussion. There are two major changes: > > 1) NotImplemented may be used by __length_hint__ to indicate that there is no > finite length hint available.
I've been thinking about this a bit more, and I think it does provide good scope for eventually adding __length_hint__ to more iterators (including map, filter and enumerate). > 2) callers of operator.length_hint() must provide their own default value, > this > is also required by the current C _PyObject_LengthHint implementation. And this makes it explicit that API users need to deal with the AttributeError/NotImplemented case, whilst making it easy to do so. Good call. > There are no provisions for infinite iterators, that is not within the scope > of > this proposal. I'll repeat my observation that remaining silent on this point is effectively identical to blessing the practice of raising an exception in __length_hint__ to force fast failure of attempts to convert an infinite iterator to a concrete container. Rather than leaving people to figure this out on their own, we may as well make it official that TypeError can be raised in __length_hint__ to block conversion to concrete containers that use a preallocation strategy. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
