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> _______________________________________