On 31 August 2016 at 13:37, Jack Diederich <jackd...@gmail.com> wrote: > On Tue, Aug 30, 2016 at 11:03 PM, Guido van Rossum <gu...@python.org> wrote: >> But myfunc.__annotations__ already exists -- PEP 3107 puts the >> signature annotations there. The problem with co_annotations is that >> annotations are evaluated (they can be quite complex expressions, e.g. >> Optional[Tuple[int, int, some_mod.SomeClass]]), while co_varnames is >> just a list of strings. And code objects must be immutable. The issue >> with rejecting duplicate annotations so sternly is the same as for the >> previous bullet. >> > > If we disallow re-assignment of types as a syntax error then the conflict > with myfunc.__annotations__ goes away for vars that share a name with the > function arguments. The fact that variables with types can't be known until > the function body executes a particular line is .. I'm not sure how to deal > with that. For modules and classes you can assert that the body at the top > indent level has been executed. For functions you can only assert that it > has been parsed. So myfunc.__annotations__ could say that the type has a > definition but only later know what the definition is.
What if we included local variable annotations in func.__annotations__ as cells, like the entries in func.__closure__? We could also use that as a micro-optimisation technique: once the type annotation cell is populated, CPython would just use it, rather than re-evaluating the local variable type annotation expression every time the function is called. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
