On Tue, Sep 1, 2020 at 9:51 AM Guido van Rossum <gu...@python.org> wrote:
> On Tue, Sep 1, 2020 at 8:20 AM Christopher Barker <python...@gmail.com> > wrote: > >> Question: it strikes me that the use case of [] for type hints is >> logically quite different than for indexing. So do they need to use the >> same syntax / dunder? >> >> I think that type hints are used in specific places, and thus the >> interpreter could know if a given [] was a type hint or an indexing >> operation, and thus could dispatch it differently. >> ... >> If it's not technically possible to make the distinction, then it's a >> non-issue, but if it is, it may be worth considering. >> > > Type hints are indeed dispatched differently, but this is done based on > information that is only available at runtime. Since PEP 560, for `x[y]`, > if no `__getitem__` method is found, and `x` is a type (class) object, and > `x` has a class method `__class_getitem__`, that method is called. > Extending this with keyword args is straightforward. Modifying the compiler > to generate different bytecode for this case is essentially impossible. > Thanks -- then that answers my question -- no it's not technically possible. Oh well. -CHB -- Christopher Barker, PhD Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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