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How many lines of C it takes to execute a + b in Python

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Re: How many lines of C it takes to execute a + b in Python

#151

Post by andai »

steveklabnik wrote: post #147
andai wrote: post #136

Earlier quoted context omitted.

Can someone explain what exactly it is about Python's design that makes it slow? What changes would have to be made to speed it up? Obviously changing its core design now would break things, but my question is, can we can imagine an alternate universe Python that's as close as possible to our Python, except really fast? What would be different?

I am going to answer this question in a roundabout way: first showing examples of different code gen in Rust, because it is more straightforward, but then I will reach for an example with Ruby, because I know it better than Python, but I believe it is similar enough that you will get the gist. If I write a function like this in Rust: pub fn add(x: i32, y: i32) -> i32 { x + y } this will compile to this assembly (on x…

Thanks. That's fascinating about Ruby, I'll have to look into that.

I'm not an expert on Python but I don't see how Python is significantly more dynamic than e.g. JavaScript. I think PyPy and JS performance is comparable (or at least within the same order of magnitude), so I think it largely comes down to implementation, i.e. prioritizing performance.

I think if it had been Python (or Ruby for that matter) in the browser instead of JS, it would run about as fast as JS does today.

Re: How many lines of C it takes to execute a + b in Python

#152

Post by a1369209993 »

Smaug123 wrote: post #125
heyodai wrote: post #118

Earlier quoted context omitted.

Yeah, that message is a pet peeve of mine. Like, you know what I'm trying to do.

It sort of doesn't! It's just doing exactly the same thing it would do with any other identifier: it's printing its `repr`. Try `repr(exit)`!

More to the point, try `[len,exit,repr]`. Consider what would happen if `exit.__repr__()` did terminate the program.

Re: How many lines of C it takes to execute a + b in Python

#153

Post by kazinator »

nostrademons wrote: post #112
Asraelite wrote: post #34

Earlier quoted context omitted.

This may be a somewhat uninformed opinion, but I think CPython is just straight up not particularly good software. There are a million and one optimizations that other major scripting runtimes (V8, LuaJIT, PyPy, Ruby YJit etc.) have had for years that CPython is lacking. This is by design though. CPython has never been focused on performance, that's why it's not even JIT. It optimizes for simplicity and easy interope…

It's great software for the use case that Python is intended for . Python is supposed to be glue code. You embed a scripting runtime in your application, do all the heavy lifting in C, but configure your building blocks in Python so that you can easily reconfigure them as needs change. NumPy, SciPy, TensorFlow, PyTorch, JAX, Pandas, Pillow, lxml, cjson, PyCapnP, Tornado, fast-avro, etc. all get it right. They are wra…

> for the use case that Python is intended for

Where is this single use case intent articulated, by whom, and what year was it? What is the use case?

Today, it seems that Python is pitched for almost everything, short of ethernet drivers.

Re: How many lines of C it takes to execute a + b in Python

#154

Post by kazinator »

nostrademons wrote: post #141
oivey wrote: post #131

Earlier quoted context omitted.

Arguably no one’s goal is to glue pieces of C together. That’s too abstract. Their goal is to do something like write a performant web server, maybe easily and quickly. Python’s approach is one way to do that, but there are other ways that might be better. Having to write code in two languages to solve a problem, one of which that is difficult to write and has lots of footguns, has some clear downsides.

Basically nobody's goal is to "write a performant web server" either, it's to serve data to customers quickly and efficiently . And that highlights why it may not be worth optimizing the Python web ecosystem. There are so many newer alternatives for that overall goal - Firebase, Amazon Lambda, ditching webapps for native mobile, etc - that it may not make sense to try to optimize an application server unless you work…

Nobody's goal is to serve data to customers quickly and efficiently either. It's more like, get this startup acquired and buy a ranch in New Zealand.

Re: How many lines of C it takes to execute a + b in Python

#155

Post by [deleted] »

jerf wrote: post #122
lifthrasiir wrote: post #50

Earlier quoted context omitted.

Unfortunately Python's innard is much more complicated than most expectations. You have named JS and Lua, but those languages never have "magic" methods---JS instead has prototypes and more recently proxies, while Lua has metatables. Ordinary objects aren't magic in this sense, and conversely magical objects are generally deliberate choices in those languages. But Python's magic `__dunder__` methods are everywhere in…

In the late 1990s and early 200xs, there were a lot of claims that there was no such thing as a "slow language", that all languages can be run as quickly as C if you just built a sufficiently smart compiler and/or runtime. I haven't heard anyone make this claim in a while. The inability to speed up Python beyond a certain point despite a lot of clever approaches taken was probably a good chunk of the reason, the rema…

[deleted]

Re: How many lines of C it takes to execute a + b in Python

#156

Post by layer8 »

whizzter wrote: post #46
BD103 wrote: post #37

This was quite interesting, but I’m disappointed it didn’t mention how many lines in C it actually took to run. Perhaps a profiler might help calculate this?

If you read the article you can see that some codepaths can invoke Malloc with all the follow-on effects like Kernel boundary crossings that this implies, it's thus quite random.

Since malloc() is a standard C library function, it would be okay to not count its implementation (which isn’t necessarily written in C).

Re: How many lines of C it takes to execute a + b in Python

#157

Post by fullspectrumdev »

wongarsu wrote: post #145
esafak wrote: post #132

Earlier quoted context omitted.

"Tech debt doesn't matter!" "We're going to redesign it the right way after we get this version out the door!"

Arguably those redesigns might have happened if the Python 2->3 transition hadn't received a decade of extremely vocal pushback

What’s funny is the breaking change that caused us the most headaches with 2->3 was the changes to fucking print.

I’m still finding broken print as a statement instead a function issues in codebases, somehow.

Re: How many lines of C it takes to execute a + b in Python

#158

Post by MR4D »

kazinator wrote: post #153
nostrademons wrote: post #112

Earlier quoted context omitted.

It's great software for the use case that Python is intended for . Python is supposed to be glue code. You embed a scripting runtime in your application, do all the heavy lifting in C, but configure your building blocks in Python so that you can easily reconfigure them as needs change. NumPy, SciPy, TensorFlow, PyTorch, JAX, Pandas, Pillow, lxml, cjson, PyCapnP, Tornado, fast-avro, etc. all get it right. They are wra…

> for the use case that Python is intended for Where is this single use case intent articulated, by whom, and what year was it? What is the use case? Today, it seems that Python is pitched for almost everything, short of ethernet drivers.

From https://www.python.org/about/ (mouse over the "About" menu) :

'Python is a programming language that lets you work more quickly and integrate your systems more effectively.'

Re: How many lines of C it takes to execute a + b in Python

#159

Post by lmm »

andai wrote: post #151
steveklabnik wrote: post #147

Earlier quoted context omitted.

I am going to answer this question in a roundabout way: first showing examples of different code gen in Rust, because it is more straightforward, but then I will reach for an example with Ruby, because I know it better than Python, but I believe it is similar enough that you will get the gist. If I write a function like this in Rust: pub fn add(x: i32, y: i32) -> i32 { x + y } this will compile to this assembly (on x…

Thanks. That's fascinating about Ruby, I'll have to look into that. I'm not an expert on Python but I don't see how Python is significantly more dynamic than e.g. JavaScript. I think PyPy and JS performance is comparable (or at least within the same order of magnitude), so I think it largely comes down to implementation, i.e. prioritizing performance. I think if it had been Python (or Ruby for that matter) in the bro…

> I'm not an expert on Python but I don't see how Python is significantly more dynamic than e.g. JavaScript.

JS has much less in the way of magic methods that can affect "normal" object behaviour, and it doesn't have metaclasses in the way that Python does at all. Most of this customization goes unused most of the time, but the runtime still has to handle it in case it's being used this time.

Re: How many lines of C it takes to execute a + b in Python

#160

Post by tesdinger »

nostrademons wrote: post #112
Asraelite wrote: post #34

Earlier quoted context omitted.

This may be a somewhat uninformed opinion, but I think CPython is just straight up not particularly good software. There are a million and one optimizations that other major scripting runtimes (V8, LuaJIT, PyPy, Ruby YJit etc.) have had for years that CPython is lacking. This is by design though. CPython has never been focused on performance, that's why it's not even JIT. It optimizes for simplicity and easy interope…

It's great software for the use case that Python is intended for . Python is supposed to be glue code. You embed a scripting runtime in your application, do all the heavy lifting in C, but configure your building blocks in Python so that you can easily reconfigure them as needs change. NumPy, SciPy, TensorFlow, PyTorch, JAX, Pandas, Pillow, lxml, cjson, PyCapnP, Tornado, fast-avro, etc. all get it right. They are wra…

> I was briefly tempted to write an API-compatible reimplementation of Django with the core in C++ when I left Google, but by then Django (and server-side web programming) was already falling out of favor, and if you're just shipping JSON to a SPA you can use cjson with any number of fast wsgi or asgi gateways.

I like Django. I need to process data on the server side and like to write that in python because it is more convenient than C. I also built my GUI in Django without knowing JavaScript. "just shipping JSON" seems like a different use case.

I have a piece of hardware (a laboratory hardware switch) that exposes a REST API for CRUD. I wanted to build a GUI that formats and summarizes information and offers convenient control. The data is small enough so that python can process it without becoming the bottleneck. I used Django ORM to model the data and django forms with htmx for the GUI. Authentication was easily added to Django.

The ORM part was a bit painful as Django forms expect a queryset and a queryset is not be the result of a raw sql query. There is a way to feed list of tuples into a choices argument but I decided against that , and instead dumbed down my query so I was able to write it as an django ORM language query.

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