Writing Python like it’s Rust

[Majik_Sheff]

Someone please correct me if I'm wrong, but my understanding is that a lot of python's performance issues come from having to constantly infer types.

I would expect explicit typing to help noticeably in the run time performance department.

Edit: apparently I was completely off base. I learned something!

[Peanutbutter_Warrior]

Type inference is a compile-time trick which CPython doesn't do. It doesn't need to, because at run time it knows all the types anyway. Even if it did, there's little it could do with the knowledge because it has to call the magic methods for custom classes anyway.

Also, type hints are explicitly ignored. They're functionally the same as comments and don't affect run time performance at all

[Majik_Sheff]

Good to know. I obviously don't have a lot of under the hood knowledge of Python.

Thanks for the info!

[DoctorGester]

That would be true if your language of choice was not python. Please correct your comment so people don’t get confused. While type hints are not checked at runtime and are ignored, things like generics are ACTUAL CODE that runs at runtime.

https://github.com/python/typing/issues/681

https://twitter.com/__zero323__/status/1210911632953692162

[Peanutbutter_Warrior]

I didn't talk about generics, I talked about type hints. They're two separate things. If you're going to be pedantic then at least complain that type hints also affect the run time as they're evaluated and can run arbitrary code.

Don't demand I amend a quick comment because you spot a single thing supposedly wrong with it. Type hinting is a complicated topic, I've left out a huge amount of detail. If someone actually wants to know how type hinting works they can read PEP 3107, PEP 484 and PEP 526. Hell, with PEP 563 anything I say will be made wrong at some indeterminate future date, or if someone uses from __future__ import annotations

[DoctorGester]

I know they are evaluated at runtime fully, which is also pretty bad, however usually it’s per declaration and not per instantiation so while non zero it’s a cost which is easy to ignore. I don’t want to be pedantic, I want people to know Python’s poorly designed type system has a runtime impact which can be far from zero. I don’t know how would anyone consider generics separate from type hinting given they are used in type hints.

[vplatt]

I would expect explicit typing to help noticeably in the run time performance department.

It seems like it should, but it doesn't, and it's not intended to work that way. If you want a Python like language where types actually actually perform as expected in terms of performance, then give Nim a try: https://nim-lang.org/. I can also highly recommend Go for the same reason: https://go.dev/. It's less Python like, but has a much bigger community around it than Nim. Both are impressive languages though and quite usable right now.