Terry J. Reedy added the comment: In #12159, Victor correctly labelled this an implementation (IE, CPython) detail (limitation). I don't believe any implementation has to limit the range of len(). So the question is whether we should add a CPython implementation limit note, including the possibility of OverflowError, and if so, to both len() and __len__() entries. I am not sure of the current doc policy. The second sentence of the len entry is out of date. " The argument may be a sequence (string, tuple or list) or a mapping (dictionary)." Sets and any collections with a size (__len__ method) can also be arguments. I am not sure how to revise that either. ---------- nosy: +benjamin.peterson, georg.brandl, haypo, terry.reedy stage: -> needs patch versions: +Python 3.2, Python 3.3 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Camilla Montonen added the comment: The deficiency noticed by Terry has been at least partially corrected in the len() docs https://docs.python.org/2/library/functions.html#len Return the length (the number of items) of an object. The argument may be a sequence (such as a string, bytes, tuple, list, or range) or a collection (such as a dictionary, set, or frozen set). It doesn't mention the fact that the collection has to implement __len__, but I suppose that might be obvious to experienced Python users (isn't obvious to a beginner like me, though). So perhaps this might be a welcome clarification. The issue regarding OverflowError raised by Rostyslav still remains unresolved. ---------- nosy: +Winterflower _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Martin Panter added the comment: Issue 10289 proposes to link from len() to __len__() in the documentation. I think the limitation only needs to be documented for __len__(); there are other ways to invoke it as well. ---------- nosy: +martin.panter _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Terry J. Reedy added the comment: Has or will builtin classes be modified to follow advice to include a separate __bool__? In 3.6.1,

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r = range(19**100) bool(r) Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> bool(r) OverflowError: Python int too large to convert to C ssize_t

---------- nosy: +serhiy.storchaka versions: +Python 3.7 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Serhiy Storchaka added the comment: New changeset 85157cd89a6edac347a5b6871fcf20c500c6fbbf by Serhiy Storchaka in branch 'master': bpo-15718: Document the upper bound constrain on the __len__ return value. (#1256) https://github.com/python/cpython/commit/85157cd89a6edac347a5b6871fcf20c500c... ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Changes by Serhiy Storchaka <storchaka+cpython@gmail.com>: ---------- pull_requests: +1373 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Serhiy Storchaka added the comment: New changeset f2ed2858eea7569c8915b3611ca5ec92ae10b17f by Serhiy Storchaka in branch '3.6': [3.6] bpo-15718: Document the upper bound constrain on the __len__ return value. (GH-1256) (#1259) https://github.com/python/cpython/commit/f2ed2858eea7569c8915b3611ca5ec92ae1... ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Serhiy Storchaka added the comment: New changeset bfc7dff63b9b30371e3423a5c35ccda2f3b52218 by Serhiy Storchaka in branch '2.7': [2.7] bpo-15718: Document the upper bound constrain on the __len__ return value. (GH-1256). (#1261) https://github.com/python/cpython/commit/bfc7dff63b9b30371e3423a5c35ccda2f3b... ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15718> _______________________________________

Change by Zac Hatfield-Dodds <zac.hatfield.dodds@gmail.com>: ---------- pull_requests: +17340 pull_request: https://github.com/python/cpython/pull/17934 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue15718> _______________________________________