[issue34494] simple "sequence" class ignoring __len__

Raymond Hettinger added the comment: I concur with Josh. This matches the documented behavior and isn't a bug. Marking as closed. There are potentially two ways to stop sequence iteration, either by using len or by waiting for IndexError. Python uses the latter to allow lists to be

[issue34494] simple "sequence" class ignoring __len__

Josh Rosenberg added the comment: That's the documented behavior. Per https://docs.python.org/3/reference/datamodel.html#object.__getitem__ : >Note: for loops expect that an IndexError will be raised for illegal indexes >to allow proper detection of the end of the sequence. The need for

[issue34494] simple "sequence" class ignoring __len__

Change by Raymond Hettinger : -- assignee: -> rhettinger nosy: +rhettinger ___ Python tracker ___ ___ Python-bugs-list mailing

[issue34494] simple "sequence" class ignoring __len__

Eric Wieser added the comment: What I think I find surprising is that I'd expect the sequence protocol to be defined by `__getitem__` and `__len__`, and for `__iter__` to be inferred as: def __iter__(self): for i in range(len(self)): yield self[i] But in reality it

[issue34494] simple "sequence" class ignoring __len__

Change by Eric Wieser : -- nosy: +Eric.Wieser ___ Python tracker ___ ___ Python-bugs-list mailing list Unsubscribe:

[issue34494] simple "sequence" class ignoring __len__

Prudvi RajKumar Maddala added the comment: I think it should hang, since we are not throwing any StopIteration exception to break the infinite loop -- nosy: +prudvinit ___ Python tracker

[issue34494] simple "sequence" class ignoring __len__

New submission from Tyler Reddy : Downstream in NumPy we've noticed that a "sequence" object defined as below will hang (infinite __getitem__ calls) if we try to turn it into an array. The same holds in CPython for converting it to a list: class OneList: def __len__(self): #