New submission from Antti Haapala: The doc reference/expressions.srt says that
> For user-defined classes which do not define __contains__() but do > define __iter__(), x in y is True if some value z with x == z is > produced while iterating over y. If an exception is raised during the > iteration, it is as if in raised that exception. and > Lastly, the old-style iteration protocol is tried: if a class defines > __getitem__(), x in y is True if and only if there is a non-negative > integer index i such that x == y[i], and all lower integer indices do > not raise IndexError exception. (If any other exception is raised, it > is as if in raised that exception). The documentation doesn't match the implementation, which clearly does `x is y or x == y` to check if `x` is the element `y` from a container. Both the `__iter__` and the index-iteration method test the elements using `is` first. While the document says that `x is x` means that `x == x` should be true, it is not true for example in the case of `nan`: ---------- assignee: docs@python components: Documentation messages: 298671 nosy: docs@python, ztane priority: normal severity: normal status: open title: Docs should say that `x is z or x == z` is used for `x in y` in containers that do not implement `__contains__` type: enhancement _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue30969> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
