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Are you expected to run five Python type-checkers now?(pyrefly.org)
47 points by ocamoss 3 hours ago | 24 comments
dsign 34 minutes ago | parent | next [-]

If you are going to be super-strict with type-checking, wouldn’t it be best to switch to a statically typed language and get the performance gains as well?

pmontra 19 minutes ago | parent | next [-]

Hallelujah, that's always been my position. To the static typing folks: leave my dynamically typed languages alone and go coding with something that really suit your needs. If the answer is that Python, Ruby, JS, whatever are really much more pleasant to code with, my reply is that they are so precisely because we don't have to type type definitions. Tradeoffs.

ocamoss 28 minutes ago | parent | prev | next [-]

Running more type checkers isn't really about strictness. The main benefit to library maintainers is to make sure that their APIs are compatible with whatever tools their users run.

This wouldn't really be an issue for most other languages, but Python's typing ecosystem is uniquely fragmented, with only partial standardization between several popular tools.

pohl 3 minutes ago | parent [-]

It isn't about [thing I object to], it's about [same thing with more palatable phrasing].

SatvikBeri 18 minutes ago | parent | prev [-]

What statically typed language would you suggest for machine learning and large data pipelines? I don't love Python, but it has by far the largest ecosystem.

shermantanktop 23 minutes ago | parent | prev | next [-]

That blog needs to run a AI checker. Content aside, a lot of the writing is pure AI style.

> The type checking that matters most (and why you've probably got it backwards)

Honestly, I don’t care if the author got some AI help. But that click-bait style is ubiquitous and obnoxious.

kingstnap 26 minutes ago | parent | prev | next [-]

The fact that this article seems to honestly recommend people run 5 different type checkers on library test suits really reflects the tacked on feeling of Python typing.

voidUpdate an hour ago | parent | prev | next [-]

> "In Python, any method __eq__ is expected to return bool, and if it doesn't, then we need to explicitly tell type-checkers to ignore the type error. This function in Polars can also return different types depending on the inputs, thus requiring overloads."

Why would you ever want a == b to not return a bool??

EDIT: Yes, I understand that you can do element-wise equality checks on numpy arrays now

vitamark 41 minutes ago | parent | next [-]

There are examples like ORM query builders (something like `User.id == user_id` should not return a boolean, but rather some inspectable query part), multi-value comparisons (e.g. numpy arrays and views which could also be used as masks for indexing)

In general, when you get your hands on operator overloading you get a bunch of various quirky applications for each. Some dunder methods have strict runtime-level rules (e.g. __hash__ or __len__), some don't

olooney 39 minutes ago | parent | prev | next [-]

It could return a vector or a deferred expression? In polars, for example, operations on `pl.col` return `Expr` objects that are used to build queries, not immediately evaluated:

    df.filter(pl.col("status") == "active")
In numpy, `x == y` return a boolean vector of the same shape as x and y, comparing them element-wise.
samsartor 41 minutes ago | parent | prev | next [-]

Elementwise equality! Given two dataframe columns or ndarrays, users often expect `==` to give out a column or ndarrays of bools (like `+`, ``, `*, `&`, and just about every other binary operator).

datsci_est_2015 an hour ago | parent | prev | next [-]

One example is if an and b are arrays (e.g. numpy arrays) it’s not unreasonable for dunder eq to return an array of booleans.

Another example might be if you have a domain specific representation of equality (e.g. class Equality)

voidUpdate 43 minutes ago | parent [-]

I can see the first one making sense, but why would you need a representation of equality other than "yes, these are equal" and "no, these are not equal"?

datsci_est_2015 37 minutes ago | parent [-]

Well personally I’m not a fan of turning everything into an object, but if you have properties or methods that exist upon the concept of Equality you might want to encode directly onto a class. Maybe in a domain where “Equality” is an important concept, like mathematics or even something like accounting.

Could enable a different interface into approximate equality for floating point numbers: Equality.approximate(iota: float) -> bool

xemdetia an hour ago | parent | prev | next [-]

I thought JavaScript language equality quirks was seen as problematic not a missing feature in Python.

voidUpdate 42 minutes ago | parent | next [-]

At least in javascript, it tells you if things are equal or not. In python, apparently you could answer if A is equal to B with "beans" or 17 or ['a']

throwaway894345 23 minutes ago | parent | prev [-]

Python never met a footgun it didn’t need to adopt. In this case, however, it’s not equality checks, but operator overloading. I was a Python developer for a decade before switching to Go and life on this side is so much better.

throwaway894345 25 minutes ago | parent | prev [-]

IIRC, SQLAlchemy overloads this to return an object that represents an equality check in SQL. Because it was returning an object, it was always evaluating to True, because of another of Python’s footguns: truthiness/falsiness. This was a decade ago, and these particular footguns were not even remotely the biggest culprits in our bug backlogs (another honorable mention includes accidentally calling a sync function in an async context, causing timeouts in unrelated endpoints and leading to cascading system failure).

blahgeek 26 minutes ago | parent | prev | next [-]

> Prioritise running as many type-checkers as possible on your test suite. Run at least one on your source code.

There are two types of tests: those that test against the public API, and those that test internal codes with various mocks and fakes. I think the vast majority of unit tests is the latter one, in which case the suggestion does not really make sense.

woeirua an hour ago | parent | prev [-]

With agents it no longer makes sense to tie yourself to Python's archaic development experience. How many type checkers are there? Package managers? Don't even get me started on cross-platform deployment.

Strongly typed, compiled languages have never been easier to use, and agents reap huge benefits from the tight feedback loop that the compiler provides. Moreover the benefits of the Python ecosystem are less significant today than anytime in the past 20 years. Need something that's only available in Python? Just point some agents at it and you can port it.

datsci_est_2015 42 minutes ago | parent | next [-]

> Just point some agents at it and you can port it.

Don’t think we’re there yet, otherwise we would see a bunch of forks of major libraries to alternative languages - and not just Python. There’s still too much risk of insidious errors and bugs.

voidUpdate an hour ago | parent | prev [-]

What about the several people worldwide who don't want to use LLMs to program?

cryptonym 40 minutes ago | parent [-]

They also "reap huge benefits from the tight feedback loop that the compiler provides".

When something is easier/requires less context, it tends to work well for both human and LLM.

vips7L a minute ago | parent [-]

I've noticed this a lot in LLM generated Java. Since it doesn't know what can or can't be null it tends to wrap everything in Optional<T>. Super strong type systems are becoming even more important.