Nick Coghlan added the comment: Many algorithms that require a sequence only need __len__ and __getitem__. The term "sequence" is used to distinguish such containers from mere iterables that only provide "__iter__" (and may be consumed by iteration). The glossary entry covers this use of the term. collections.abc.Sequence is a much richer interface, which defines many additional operations beyond those iteration, indexing and slicing. Types which implement that full API can be registered explicitly (or else an application can define it's own custom ABC for a subset of the Sequence API). However, the glossary entry should link to http://docs.python.org/3.3/library/stdtypes#sequence-types-list-tuple-range to expand on the second meaning of the term. PySequence_Check is an unreliable guide (albeit not quite as unreliable as PyMapping_Check) that checks a CPython implementation detail. ---------- assignee: -> docs@python components: +Documentation -Library (Lib) nosy: +docs@python, ncoghlan stage: -> needs patch title: collections.abc.Sequence shoud provide __subclasshook__ -> Missing cross-reference in sequence glossary entry type: -> enhancement _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue16728> _______________________________________