On 09/14/2017 12:08 PM, Ivan Levkivskyi wrote:
On 14 September 2017 at 01:13, Guido van Rossum wrote:
That last sentence is a key observation. Do we even know whether there are (non-toy) things that you can do *in principle* with __class__ assignment but which are too slow *in practice* to bother? And if yes, is __getattr__ fast enough? @property?I myself have never implemented deprecation warnings management nor lazy loading, so it is hard to say if __class__ assignment is fast enough. For me it is more combination of three factors: * modest performance improvement * some people might find __getattr__ clearer than __class__ assignment * this would be consistent with how stubs work IMO we're still looking for applications. How about this def allow_forward_references(*allowed): caller_globals = sys._getframe().__globals__ def typing_getattr(name): if name in allowed: return name raise AttributeError(...) caller_globals.__getattr__ = typing_getattr from typing_extensions import allow_forward_references allow_forward_references('Vertex', 'Edge') T = TypeVar('T', bound=Edge) class Vertex(List[Edge]): def copy(self: T) -> T: ... class Edge: ends: Tuple[Vertex, Vertex] ... Look mum, no quotes! :-)
For comparison's sake, what would the above look like using __class__ assignment? And what is the performance difference? -- ~Ethan~ _______________________________________________ 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
