Introduce a boundary parameter for typing.get_type_hints when used with a class object
In one of my projects I'm reusing class-level type annotations to identify relevant attributes for serialization, e.g. similar to the following: attrs = {name: getattr(obj, name) for name in get_type_hints(type(obj))} This is convenient because it merges the type annotations from the various stages in the class hierarchy, e.g. class Base: a: int class Derived(Base): b: str results in `attrs == dict(a=..., b=...)`. However it becomes inconvenient if external base classes are involved that define their own, unrelated type annotations, e.g. class External: # from some other distribution unrelated: float class Base(External): a: int It would be helpful if `get_type_hints` had a `boundary` parameter that, when used with a class object, determines the upper boundary for the MRO. So it could be used in the following way: get_type_hints(type(derived_obj), boundary=Base) to exclude any type annotations further up the class hierarchy (including the ones from `Base`). Regarding the implementation this would effectively skip over base classes in the reverse MRO until it reaches the `boundary`. What do you think?
This definitely feels to me like though if an oddball case that "write your own function" seems like the best solution. I accept the OP needs it, but I have trouble imagining that many others would. On Tue, Aug 4, 2020, 7:42 AM Dominik Vilsmeier <dominik.vilsmeier@gmx.de> wrote:
On Wed, Aug 5, 2020 at 12:25 AM Dominik Vilsmeier <dominik.vilsmeier@gmx.de> wrote:
In that case I recommend that you create a bpo issue about adding it and submit a PR to resolve the issue. I think the public API should have the same defaults for globalns and localns as get_type_hints(), and it should probably not expose the recursive_guard argument. Since this is a new feature and the 3.9 release is already closed for new features, this can be added in 3.10 -- in earlier releases you'll have to use `_eval_type`. (It does not seem important enough to add it to the typing_extensions module.) -- --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-c...>
This definitely feels to me like though if an oddball case that "write your own function" seems like the best solution. I accept the OP needs it, but I have trouble imagining that many others would. On Tue, Aug 4, 2020, 7:42 AM Dominik Vilsmeier <dominik.vilsmeier@gmx.de> wrote:
On Wed, Aug 5, 2020 at 12:25 AM Dominik Vilsmeier <dominik.vilsmeier@gmx.de> wrote:
In that case I recommend that you create a bpo issue about adding it and submit a PR to resolve the issue. I think the public API should have the same defaults for globalns and localns as get_type_hints(), and it should probably not expose the recursive_guard argument. Since this is a new feature and the 3.9 release is already closed for new features, this can be added in 3.10 -- in earlier releases you'll have to use `_eval_type`. (It does not seem important enough to add it to the typing_extensions module.) -- --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-c...>
participants (3)
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David Mertz -
Dominik Vilsmeier -
Guido van Rossum