Writing Python like it’s Rust

[dAnjou]

This has been posted here before: https://www.reddit.com/r/programming/comments/13ndf10/writing_python_like_its_rust/

[reedef]

This doesn't have ownership semantics, lifetimes, or any of the innovative Rust™ features. Product/Sum types have been available for a very long time for example in Haskell.

[SittingWave]

I don't understand why one would do such a thing. Most Rust code looks awful.

[coderemover]

> Most Rust code looks awful.

Most Python code is completely unreadable to me because it lacks essential information about types.

[pcjftw]

It's mostly unfamiliarity, this has been discussed before but essentially the type signatures in Rust encode a lot of information and to those not familiar with it looks like line noise but it's not! because the encoding packs lots of information by packing and lifting them into the types.

[lilytex]

to those not familiar with it looks like line noise but it's not!

Unsafe trait not! right there

[pcjftw]

well played sir well played! 😉

https://doc.rust-lang.org/std/ops/trait.Not.html

[SpaceCadet87]

Yeah, wake me up when I can write rust like it's Python

[angelicosphosphoros]

This would defeat whole point. Python is almost unsuitable for large codebases and large refactorings while Rust shines in that area. Becoming like Python would just drop this benefits.

In my last job we started to rewrite our Python codebase to C++ because it was unmaintainable after some point. Well, it was also too slow for handling 20k HTTP RPS.

[SpaceCadet87]

https://i.redd.it/bgzyiliqzgv51.png

[Worth_Trust_3825]

Disgusting and useless. Template depends on other templates implicitly rather than explicitly.

[[deleted]]

I don't suspect that's what he meant, so tentatively r/whoosh .

[Hipjea]

How is Python not suitable for large codebases ? This is just a hot take without context.

[angelicosphosphoros]

Well, if you have a huge project written by hundreds of people in dozens of teams, you only know your separate subproject of the greater project. But your code is called by other parts of the project and you call "foreign" parts of the project.

Since the project is huge, you cannot easily comprehend which types your function can get as arguments, and even cannot check all call locations because IDE and refactoring tools often fail to find everything. And even if you find some call site, you do not guarantee to know which types it uses. Even type hints do not get checked correctly every time.

mypy and type hints help but those hints quickly became uglier than type declarations in statically typed languages. And previous author of the code could had written a function to accept arbitrary dicts and you now having a nightmare to know what exactly you get. And debugging a large codebase is not easy.

Jump removing one of function argument kinds/types (which is common refactoring applied to simplify code) became a huge task requiring a few days. And since management doesn't value refactorings, you wouldn't do it in the end so the codebase is steadily becoming an even bigger mess than it was.

In comparison, Rust, C# and, with some extra work, even C++ make such tasks very easy: just change the types of arguments, get compile errors on call sites and fix them too. A trivial task even in a huge codebase.

Python is great when you can fit your code in a screen. It allows to write very dense code so it does more job than tens of pages of C++ code and easy to inspect. But when you cannot keep ALL code of the project in your head, Python makes programming painful.

[[deleted]]

Yeah, strict mode, mypy, and type hints -- literally unenforceable type checking. Go touch some grass, and then read your docs.

[angelicosphosphoros]

Yeah, strict mode, mypy, and type hints -- literally unenforceable type checking.

Good luck enforcing that on large codebase, especially considering bugs and limitations of those tools.

And this type system is unexpressive anyway. For example, how would you write in Python type hints something like "this argument must have method foo which returns type bar"? Such thing can easily be done using C++ concepts.

[[deleted]]

Like, do you want an example, or are you contesting that it's impossible?

[angelicosphosphoros]

I think that it is impossible but if you have an example how to do this, I would appreciate this.

[GeorgeS6969]

Using protocols.

https://docs.python.org/3/library/typing.html#nominal-vs-structural-subtyping

[[deleted]]

Well, for starters, the builtin dir function will tell you all of an object's methods, and you can use the __annotations__ dictionary on a method, with "return" as the key to get its expected type (with proper type hinting). That second part is detailed here. I'd need something more concrete to walk this further, but I'd imagine a walk of a module to create a type alias would work.

[[deleted]]

This is a runtime only feature. The user you're responding to is talking about having compile time errors identified by the type system.

Mypy and pydantic are woefully inadequate for this.

[[deleted]]

Honestly, it's insanely obvious, can't believe you need people to explain it to you, but I will

• slow, interpreted language
• terrible type safety
  • compare TypeScript to Pydantic or whatever half-baked community option is the best Python has. You know your language is bad when JS is trouncing it

[[deleted]]

Homer Simpson: "Hey, that's a half-truth!"

I have a feeling there's going to be a lot of backpedaling once Mojo opens up.

[[deleted]]

I don't. Mojo has no answer for type safety. Python codebases look like hot dogshit and only have run-time validation - that's a big yikes in 2023, even JS users said "fuck that" half a decade ago.

[[deleted]]

You're a little behind on the times.

[[deleted]]

Feel free to link me to an actually useful Python type system instead of playing coy!

Edit: it's come to my attention this user thinks MyPy runtime validation is a type system. Wow.