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 The second sentence of the len entry is out of date.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> _______________________________________