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Comment by zelly | Hacker News Reader

Type hints don't help performance either because the interpreter discards them. The hints are not enforced by CPython, so you now need a build tool instead of just running the script. The whole point of PEP 484 seems to be to enable autocomplete in Visual Studio Code.

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> The whole point of PEP 484 seems to be to enable autocomplete in Visual Studio Code.

It's to enable tooling, but not just autocomplete. The main purpose of typing is preventing type-related bugs, though making editor autocompletion and other editor information more robust is a not-insignificant additional benefit.

PEP 484 (created 29-Sep-2014, accepted 22-May-2015) wasn't motivated by VS Code (announced April 29, 2015).

PyCharm understands type hints for years now. Without using mypy btw. VSCode should be able to that, there should be one or more (either finished or half baked) plugins for it.

Edit: Microsoft Python Language Server has it (i read)

> Type hints don't help performance either because the interpreter discards them.

With CPython they don't. Cython actually uses annotations to optimize the generated code.

That's literally a different language though, but I get your point. CPython is the worst implementation.

It has nothing to do with any particular editor, it is for autocomplete and build time type checking in any editor and type checking in people's build chains.

Your code should get type checked whenever you run tests and can help reveal subtle bugs (for example, allowing Optional but not handling None in all code paths)

Another great value of running mypy on your code is that you ensure it can be compiled as a whole!

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