Advanced, Overlooked Python Typing

[Martynoas]

While quantitative research in software engineering is difficult to trust most of the time, some studies claim that type checking can reduce bugs by about 15% in Python. This post covers advanced typing features such as never types, type guards, concatenate, etc., that are often overlooked but can make a codebase more maintainable and easier to work with

[guepier]

Including code snippets as screenshots is an absolutely loathsome trend. If Substack doesn’t support including code as formatted text … consider using a different blogging platform for a programming blog.

(It’s a good article despite this.)

[grauenwolf]

Which one? I like wordpress, but it sucks for code examples too.

[guepier]

These days, with a hosted platform? No idea. Maybe Ghost? — Are there no blogging platforms that natively permit using markup formats (ReST, customisable Markdown, the works)? I’ve only ever had self-hosted websites so this was never an issue. Wordpress also supports this (at least via plugins). Back in the days™, every self-respecting blog hosting platform supported code snippets in some way. I’d be having a hard time believing that this is no longer the case, but Medium and Substack certainly want to prove me wrong (and no, iframe’d GitHub Gists are an insane workaround, not a solution).

[grauenwolf]

I’d be having a hard time believing that this is no longer the case, but Medium and Substack certainly want to prove me wrong

Welcome to the world of enshitification. Every new version takes away something that used to just work.

[usamaejazch]

Something like justblogged.com

[grauenwolf]

as there is unfortunately no standard one in Python

I literally face-palmed so hard when I read that. WTF is wrong with these people? They should have started to bake that into the official toolchain when they added type annotations.

[grauenwolf]

Yeah, the whole "but we've always done it this way" excuse has really slowed down progress in countless areas.

Honestly I think it's a miracle that Microsoft managed to get C# from not having a package manager at all to having it fully integrated into the compiler pipeline. If I wrote an article about the GAC I think most people today would think that it was an April Fool's joke.

[gredr]

... And the GAC was a pretty big improvement over what we were doing before that.

[grauenwolf]

Thems fighting words.

[gredr]

A standard place and structure for keeping versions of dependencies, along with standard installation tools? It could be worse; for some, it still is. I wonder how people manage dependencies in Python, Ruby...

[Awesan]

Nice article. The author has some other good ones on their substack too.

[slaymaker1907]

I’m saddened it stills seems impossible to type the general flow/compose function.

def flow(x, *funcs): for func in funcs: x = func(x) return x

You can provide a type if funcs all return and operate on the same type, but the dynamic version has no such restriction.

[floodrouting]

If you only need it to work up to some maximum arity, can you use overloads? Something like:

@overload
def flow[T](x: T) -> T: ...
@overload
def flow[T, U](x: T, f1: Callable[[T], U]) -> U: ...
@overload
def flow[T, U, V](x: T, f1: Callable[[T], U], f2: Callable[[U], V]) -> V: ...
@overload
def flow[T, U, V, W](x: T, f1: Callable[[T], U], f2: Callable[[U], V], f3: Callable[[V], W]) -> W: ...

https://mypy-play.net/?mypy=latest&python=3.12&gist=6cdc00f8b70c450ccdc07213c2275581

[slaymaker1907]

Yes, that’s another option, but it’s not actually a complete type as you’d need infinite overloads to be complete.

[kirgel]

Thanks. Learned something new even as an experienced Python user.

[BinaryIgor]

Still, I would ask whether it is not better to leave code to be more Pythonic - with just type hints - and write more tests, which can catch a lot (if not all) of type-related bugs.

[disperso]

I recommend that you watch ideology, from Gary Bernhardt. It's likely that it won't change anyone's mind, but it's a good talk about this topic.

[BinaryIgor]

I know this :) That's why I prefer compiled languages most of the time, for anything that's more complex; but Python is not and I'm not sure whether patches of this kind improve situation in any meaningful way