A Failed Experiment with Python Type Annotations

Re:A Failed Experiment with Python Type Annotations by _ZeD_ on Wednesday June 12, 2019 @01:24AM (#20161993)

This is not mypy, it's "python-the-language": the annotations are values, and, in this case, the method annotations are evaluated when encountered - which is before the end of the class. So you are trying to use a value still not defined. It's like doing something like

    def foo() -> Bar:
       ...

    class Bar:
       ...

obviously the python interpreter cannot find a "Bar" definition during the parsing of the foo function

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Re:A Failed Experiment with Python Type Annotations by BurningFrog on Friday June 14, 2019 @12:18PM (#20184192)

You're saying this is how the language works.

I'm saying the language could work differently.

The case of referring to a class inside its definition is quite different from your "Bar" case. The thing referred to is already declared, it's just not fully defined yet.

There is no logical reason I can see making it impossible for Python to honor the obvious intention of the programmer here. It seems it has just chosen not to do so. Though I'll admit I haven't thought through every weird corner case :)

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