That looks like a two-line convenience function using no private APIs, so you can easily include that in your own toolbox if you need it.
If your concern is that get_type_hints() is too slow, submit a PR that makes it faster. There's a cache built into ForwardRef, but it appears to be ineffective because a new ForwardRef instance is created each time when get_type_hints() encounters a string value. Maybe the ForwardRef instance should be stored back into `__annotations__`? On Thu, Dec 10, 2020 at 10:43 PM Paul Bryan <pbr...@anode.ca> wrote: > With PEP 563 behavior going mainstream in Python 3.10, I see some > ramifications, especially for runtime validation of type hints: > > 1. PEP 563 is changing the scope of evaluation of type hints, and in some > cases it is not feasible to move that scope to the annotated object's > globals. (I appreciate the reality that such cases would evade static type > checkers.) > > 2. The typing.get_type_hints function causes annotation(s) to be > evaluated from strings for every call, incurring a potentially significant > runtime penalty depending on how often type hints are evaluated at runtime. > > To address both of these issues, I'm proposing that a new function be > added to typing: affix_type_hints. > > I'm thinking something like this: > > > def affix_type_hints(obj, globalns=None, localns=None): > > """ > > Affixes an object's type hints to the object. > > > Type hints are affixed by first being resolved through > > get_type_hints, then by storing the result in the object's > > __annotations__ attribute. > > > If the object is a class, this function will affix annotations from all > > superclasses. > > """ > > > if hints := typing.get_type_hints(obj, globalns, localns, > include_extras=True): > > obj.__annotations__ = hints > > > > Advantages: > > 1. The time and scope of type hint affixation are under the control of the > caller. Future references can be realized before type hints are affixed. If > there is a novel local scope required to resolve the type hint, it can be > supplied in-context; future calls to get_type_hints inherit the benefit > of such pre-resolution. > > 2. Annotations will not be re-evaluated on repeated calls to > get_type_hints. > > 3. It doesn't require a change to the behavior of the get_type_hints > function. > > > Disadvantages: > > 1. Subclasses inheriting superclass annotations may be undesirable. > > 2. Monkey-patching __annotations__ may be considered an anti-pattern. > > 3. Maybe allowing re-evaluation on every get_type_hints call is > desirable? (I'd rather avoid the potential for side-effects.) > > 4. The cited example is a 2-line function; perhaps its triviality makes it > unjustified to add to the stdlib. > > > Alternatives: > > 1. A caching version of get_type_hints. It looks like > ForwardRef.__forward_value__ could actually deliver if annotations were > encoded as ForwardRef objects instead of string literals. Am I missing a > way for ForwardRef to cache evaluated values when get_type_hints is > called? > > 2. Something I haven't considered? Please let me know. > > > Paul > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/GZ7QGEABF624C6SKHUG7CWQAJ3XTJLIO/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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