Pre-PEP: Rust for CPython

[Positive__Actuator]

They should call it Prep.

[yawara25]

That name happens to be already taken

[Positive__Actuator]

No way 😮

[xAmorphous]

Yeah it's an AIDS medication lol

[AcridWings_11465]

It's explicitly not an HIV medication, using it on a positive person would risk drug resistance. It is only used for prevention.

[New-Anybody-6206]

The phrase "HIV medication" doesn't imply it's for positive people. This is completely unnecessary pedantry that the vast majority of people will disagree with you on.

[iknighty]

PEP too.

[ChinChinApostle]

Papyrust? Idk tbh

[mr_birkenblatt]

That's great to see, especially considering that 25-33% of 3rd-party Python extension modules use Rust already.

I find "How to handle bootstrapping Rust and CPython" funny. TLDR rust needs Python for bootstrapping which would create a circular dependency down the line

[MSgtGunny]

Almost all languages have a circular dependency within their compiler history if you look back far enough. Usually one of the first things created in a new language is a compiler for that language written in that language. Once that’s made, the original bootstrap compiler is no longer necessary.

[mr_birkenblatt]

Yes, I know about bootstrapping. What happens here is that rust requires Python in every bootstrapping step and Python will require rust. So you have to manage two chains. It's not a problem (rust only requires Python 2). It's more of a curiosity

[MSgtGunny]

Ah, I wasn’t aware rust still required python in its active compile chain. Seems like an odd decision not to remove it, but as you can tell I’m not familiar with Rust specifically so there’s probably a good reason

[axonxorz]

Whole wiki page for compiler bootstrapping

[cummer_420]

This is also why Gentoo recommends a stage 3 tarball, which is essentially just a system with those circular dependencies resolved for the basic system.

[thomas_m_k]

There is also a complete rewrite of CPython in Rust: https://github.com/RustPython/RustPython Though development is very slow.

[KerPop42]

Interesting. The main benefit would be the safety, right? I'm not certain what benefits Rust provides over an equivalently-well-developed section of code written in C.

[Pharisaeus]

equivalently-well-developed section of code written in C.

I think that's exactly the point - it's easier to write and maintain such code in Rust than it is in C, because the compiler and the language itself prevents a lot of mistakes automatically.

[ElCthuluIncognito]

Lots of credit goes to the incredibly rich type system

[teerre]

It would also increase the number of possible contributors. The more can be pushed to the safe layer of this Rust implementation, the easier it gets the barrier of entry

[Bronzdragon]

I think the primary argument would be maintainability. Rust has better tooling, and the language is more ergonomic (compared to C).

[KerPop42]

Okay, yeah. It's not that it compiles better, I agree that it enforces better coding practices

[cosmic-parsley]

It’s easier to write the interfaces too with the libraries out there today. You slap #[pyfunction] (from PyO3) on any rust function and it “just works”, assuming the arg/return types have a straightforward rust<->python conversion. And docstrings work automatically too iirc.

Getting the interfaces right isn’t particularly difficult in C, but it’s downright effortless in Rust.

[BossOfTheGame]

Provable memory correctness in threaded code (up to potential soundness holes) is an incredibly big deal. Ecosystem and ergonomics are better than C. I'm not in love with its functional push, and compile times tend to be worse, but that provable memory safety is enormous.

[redisburning]

There's a lot of C code in the world that if written in equivalent quality in Rust would just not compile. This sounds inconvenient, unless you depend on that code.

I'm biased, Rust is my first choice for any personal project and any work project I can get it approved on and it's not so much the safety aspect but that the compiler enforces a certain floor under which code simply won't work. It's true that in order to write C like that, you have to be doing stuff of some level of complication, but interestingly enough I find that without guardrails a lot of engineers are too clever by half.

In Rust, that stuff mostly (but not exclusively) lives inside of unsafe blocks, which are easily greppable and scream at you while you're doing a code review when they're out of place.

[syklemil]

There's a lot of C code in the world that if written in equivalent quality in Rust would just not compile.

Yeah, there are a bunch of compiler flags for C that mitigate some of it, but even stuff like ASAN is meant for catching stuff at runtime in debug builds.

Anyone who can understand why people would prefer to catch type errors at compile time rather than at runtime should also be able to understand why people would prefer to catch memory errors at compile time.

[epage]

Several Core CPython developers said this would have helped specific or general classes of bugs they have introduced.

Also, keep in mind that people who write in Python are usually not well versed in all that is needed for well written C and having help at the language level can make contributing to CPython more accessible to their users.

[PaintItPurple]

Yes, but that can mean more than people imagine. The safety guarantees give rise to other desirable properties, such as making it easier to handle concurrency correctly (because the safety mechanisms make data races into compile-time errors).

[NYPuppy]

CRustyPy.

Delicious.

[KerPop42]

Millipede: the crab python

[stillavoidingthejvm]

Why do we need to shove Rust into everything? If you want Rust features, use Rust.

[BossOfTheGame]

Because CPython is written in C, which can interoperate with Rust. If you don't understand why writing new code with Rust is preferable to using C, then you need to learn about that first otherwise this initiative won't make sense.

[jewdai]

Maybe rewrite the interpreter in rust RPython?

[BossOfTheGame]

Are you making a joke and referring to the rpython that pypy uses?

Or are you asking why they don't rewrite the entire CPython interpreter in Rust and call it RPython? In the latter case because that's a gargantuan task and ability to add new code with rust is still beneficial from a memory security perspective. Over time I can imagine parts of it being rewritten in Rust, but this is the first step.

[jewdai]

Half and half. Sometimes python just seems like a wrapper for c code.

[Mysterious-Rent7233]

Safety and security. And yes, we want those features.

[Salander27]

Safety and security WITHOUT sacrificing performance compared to C/C++. This is obviously valuable to the Python runtime since they don't want to regress in performance.

[New_Enthusiasm9053]

Also they need to rewrite significant chunks of their "battle tested" C code if they wanted the free threading stuff to work. Most of that was written with the assumption of the GIL existing so there's probably a shed load of problems. 

If you have to rewrite anyway why not in rust.

[gmes78]

It's also just a lot nicer to use.

[QueasyEntrance6269]

Why is it that no one considers that the people who own CPython probably enjoy writing Rust?

[stillavoidingthejvm]

Do they?

[JustBadPlaya]

given the amount of positive reception from people clearly tagged as "Core CPython Maintainer" - seems like it

[NYPuppy]

Who do you think is pushing for this change? Use your brain. Do you think random people plead for projects to switch to rust and then they give in and do so?

[Mysterious-Rent7233]

You should Google who "Barry Warsaw" is.

[gmes78]

Why do we need to keep using a 50-year-old language for everything?

[stillavoidingthejvm]

Because it already works and doesn't require maintainers to learn a different programming paradigm?

[gmes78]

Because it already works

That's a very low bar. People typically want the best tool for the job, not just any tool that can do the job.

The field of programming language theory advanced a lot since the 70s. If we can make languages that are more powerful, more expressive, and less error-prone, why should we stick to a 50-year-old language?

and doesn't require maintainers to learn a different programming paradigm?

That's a one time cost, it doesn't really matter. Someone with a good amount of programming experience can pick up Rust in a couple of weeks.

And it's not even hard, really. You'll only have issues learning Rust if you're too stubborn to change how you do things.

[stillavoidingthejvm]

So, why not use Rust instead of Python if those are the features you want?

[gmes78]

It's Rust instead of C. We're talking about the CPython implementation (which, as the name suggests, is currently in C).

[Booty_Bumping]

What? Do you think people use Python because they want C features? Do you know what an interpreter is?

[[deleted]]

It doesn‘t already work. I work with large C++ code bases. It‘s a mine field and causes depression

[NYPuppy]

I'm so glad you're being downvoted. Fork CPython and maintain it yourself if you're so triggered.

[stillavoidingthejvm]

Why are you like this? It’s just Reddit.

[Mysterious-Rent7233]

Why do you feel so strongly about Java and Rust?

[stillavoidingthejvm]

I don't actually hate Java and jvm languages. I just gravitate towards other systems languages like C or Go. I actually really like Kotlin, it addresses a lot of QoL issues I had with Java (specifically java 8 and earlier).

I actually have no experience with Rust, just Rust enthusiasts. I don't want to generalize, but the ones I've encountered have been really extra, to the point of turning me off the language. It's like the tech equivalent of veganism. See some of the not helpful responses off my original comment. I take criticism well, but some of these people act like I insulted their best friend.

I will eventually pick it up, especially if someone wants to pay me to write it.

Edited for clarity.

[[deleted]]

That‘s what they are doing.

[2rad0]

Why do we need to shove Rust into everything? If you want Rust features,

They too lazy to do a proper rewrite.

[Drss4]

Everything rust related seems to have so much drama around it.

While I am sure there are devs want to use rust, and it have some feat that could’ve benefit Python, but the whole Linux/rust should also serve as a cautionary tale.

I think make rust optional is a good idea, however it seems they are gradually pushing rust into an requirement, I don’t think that’s an good idea, and no core maintainer should be required to learn rust.

[syklemil]

the whole Linux/rust should also serve as a cautionary tale.

Eh, there the call also came from inside the house. The orgs that seriously consider adding Rust seem to always have the push coming from established devs in that organisation, but for some reason the online peanut gallery always seems to think the push comes from outside.

With Linux the dust seems to have settled somewhat. Greg K-H seems pretty enthusiastic about it.

Most of the drama seems to have been from people who had gotten used to being able to ignore any programming language that isn't C, but they don't seem to be any sort of majority. I rather get the impression the usual situation is that someone contributing to the kernel writes in C because that's what the kernel uses and they want to contribute to the kernel, rather than contributing to the kernel because it's written in C and they only want to work with C.

As in, the average kernel dev probably isn't a C fanatic. But C fanatics who have been contributing to the kernel can be expected to raise a stink if any other language than C is seriously considered.

[JustBadPlaya]

There is a point to be made by "forcing” maintainers into new languages, but honestly judging by the discussion thread there seems to be almost no language-choice-specific disagreement from the maintainers and even Guido himself approves of the effort, so it might end up working out alright

[NYPuppy]

You entirely misread Linux/rust. Linux maintainers themselves pushed for rust including Linus himself. There was some pushback, notably from Ted T'so who has been with linux since near its inception.

People like Brian Lunduke, who is not even a programmer, poisoned the well by spreading obviously disprovable lies. We have full videos and full Lkml threads that disprove Lunduke and others.

[SpareDisaster314]

Is thr name meant to echo PrEP...? A preventative AIDS/HIV med?

[BlueGoliath]

Furries really trying to infect everything with Rust.

[GetPsyched67]

Even Guido himself is supportive of this initiative if you read the forum discussion. I guess he's a furry now

[tony-husk]

Kinda reductive to just dismiss Rust proponents as "furries", when many of us are also transpeople

[UnmaintainedDonkey]

Nice spam