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Comment by watermelon0 | Hacker News Reader

I'm just using it to get my job done, and really couldn't imagine working with Python without it.

I'd consider static type checker as optional if you are playing around with small or throwaway scripts, but for any half serious project, it should be a requirement.

IME I don't consider it slow, and it's definitely not visibly slower than pylint, flake8, or similar tools for other languages.

Dropbox, which has one of the biggest Python codebases, uses it, and most mypy maintainers including Guido work there.

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> Dropbox, which has one of the biggest Python codebases, uses it, and most mypy maintainers including Guido work there.

Guido hasn't worked at Dropbox since 2019. He retired for a bit, but is now in the Developer Division at Microsoft.

My bad, I just checked http://mypy-lang.org/about.html, which appears to be outdated.

Yea, it may slightly slow down the initial draft due to needing to type a little bit more, but it helps speed up maintainability and readability a ton and it helps eliminate a bunch of bugs so I think it has definitely increased productivity in my experience.

The biggest problem with mypy is that it's written in python. It's slow. It needs to be rewritten in rust or go to make it faster like how js ecosystem is moving in that direction. All the tooling is moved to faster compiled languages.

mypy has implementations in other languages – PyCharm's is in Java, Facebook's Pyre's is in OCaML https://github.com/facebook/pyre-check

Those tools are not re-implementations of mypy, but their own type checkers. Pyre doesn't necessarily have all the features of mypy and vice versa.

mypy is actually compiled via mypyc, which should be a few times faster than interpreted Python https://github.com/python/mypy/tree/master/mypyc

Initial type checking with mypy is slow, but if you use mypy-daemon each check after that becomes pretty much instantaneous, even on 10M+ line code bases.

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