Mark Dickinson <dicki...@gmail.com> added the comment: [I wrote this before Serhiy posted his reply; sending it anyway, in case the doc links are useful.]
This is documented, by-design behaviour. Essentially name resolution skips class scopes. See https://docs.python.org/3/reference/executionmodel.html#resolution-of-names, and particularly the example at the end of that section, which is very similar to your example. See also: https://docs.python.org/3/reference/expressions.html#displays-for-lists-sets-and-dictionaries, and in particular this part: > However, aside from the iterable expression in the leftmost for clause, > the comprehension is executed in a separate implicitly nested scope. > This ensures that names assigned to in the target list don’t “leak” into > the enclosing scope. That "leftmost for clause" bit explains why, in the following example, the first comprehension is evaluated successfully, but the second raises a `NameError`. >>> class A: ... a = 3 ... b = [x+y for x in range(a) for y in range(3)] # okay ... c = [x+y for x in range(3) for y in range(a)] # raises ---------- nosy: +mark.dickinson -serhiy.storchaka resolution: duplicate -> not a bug stage: resolved -> superseder: improper scope in list comprehension, when used in class declaration -> _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue34517> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
