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The magic of asyncio explained

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Re: The magic of asyncio explained

#61

Post by sametmax »

mtrovo wrote: post #50
sametmax wrote: post #41

Earlier quoted context omitted.

That's because most of those tutorials have not been written by somebody actually putting something in production. I've been using asyncio for a while now, and you can't get away with a short introduction since: - it's very low level - it's full of design flaws and already has accumulated technical debt - it requires very specific best practices to be usable I'm not going to write a tutorial here, it would take me a…

Wow, really nice list, I wish I knew it before I started to work with asyncio. > stay sane, you should never, ever, have an dangling awaitable anywhere. Always get a reference on all your awaitables. Decide where in the code you think their life should end. This is the most difficult part for me, it's not trivial to know if a function you're calling is async or not without looking at the function source, specially wh…

That's why you should activate the debug features I mentioned. It will write in the console when you are calling an async thingy without getting the result from it.

Re: The magic of asyncio explained

#62

Post by luckycharms810 »

anilakar wrote: post #30

Yet another asyncio tutorial that shows you to run a few sleep tasks concurrently. Can we finally get one that shows how to do real stuff such like socket programming, wrapping non-async-compatible libraries and separating cpu-intensive blocking tasks to awaitable threads?

It is not in the style of a blog, but I put this together a few years ago to teach people how async programming works. It includes a handful of examples on generators, Coroutines, how to make use of the socket libs non blocking functionality, and how to tie them together to get the yield syntax folks are used to.

It doesn’t use any asyncio parts of python but is just meant to show what’s happening under the hood.

https://github.com/ltavag/async_presentation?files=1

Re: The magic of asyncio explained

#63

Post by sametmax »

mehrdadn wrote: post #58
sametmax wrote: post #41

Earlier quoted context omitted.

That's because most of those tutorials have not been written by somebody actually putting something in production. I've been using asyncio for a while now, and you can't get away with a short introduction since: - it's very low level - it's full of design flaws and already has accumulated technical debt - it requires very specific best practices to be usable I'm not going to write a tutorial here, it would take me a…

Awesome comment. One thing I want to point out to those reading is that the nursery thing is an instantiation of the more general principle of, if you're finding your code is getting convoluted, it's likely that you're missing a noun . I can't explain this as well as others have, so see this comment: https://news.ycombinator.com/item?id=16468796

I just love this comment.

I'm going to steal it for my next training on how to design an API.

When you are a computer scientist, you want to think about your data structures so badly first. It fits your brain so well, and it's easier to understand a program from them than the rest of the code.

But it's a trap.

Re: The magic of asyncio explained

#64

Post by mehrdadn »

sametmax wrote: post #63
mehrdadn wrote: post #58

Earlier quoted context omitted.

Awesome comment. One thing I want to point out to those reading is that the nursery thing is an instantiation of the more general principle of, if you're finding your code is getting convoluted, it's likely that you're missing a noun . I can't explain this as well as others have, so see this comment: https://news.ycombinator.com/item?id=16468796

I just love this comment. I'm going to steal it for my next training on how to design an API. When you are a computer scientist, you want to think about your data structures so badly first. It fits your brain so well, and it's easier to understand a program from them than the rest of the code. But it's a trap.

Yes, PLEASE do!! :) I've been dying myself to get chances to teach these kinds of ideas! Hardly anyone seems to teach this kind of thoughtful analysis. Eric Lippert deserves an enormous amount of credit for writing this series in particular -- trying to explain these ideas coherently has been a massive struggle for me, let alone trickling them down to a small example that's easy to digest. He's a really awesome guy I look up to... I've learned so much from his writing (this is only one example of many).

Re: The magic of asyncio explained

#65

Post by zbentley »

heavenlyblue wrote: post #51
tlrobinson wrote: post #24

This is essentially how modern JavaScript works, in particular with the addition of async/await syntax [1] (which was originally from C#, I think), but it's been possible with libraries like task.js, co, and Bluebird [2] since generator functions were available (either natively or via transpiling). The main difference is in JavaScript the event loop is automatic and hidden, and asynchronous IO is the default, so it's…

Automatic and hidden? JS had never provided any proper tools for async debugging. Can I please access a list of all async threads running at this point of time? Surely you can shoot yourself in the foot, but you can also do many other things JS never even attempted to fix. Please stop this JS fanboyism. This is a python thread.

I don't think it's "fanboyism" to point out one of the most important contemporaries of the Python async/await system, which is also one of the leading platforms that enables that pattern in production today.

And yes, you can access a list of async operations (not "threads"; some of them are threads and some of them are multiplexed IO selectors/pollers--know the difference) running at any point in time: https://www.html5rocks.com/en/tutorials/developertools/async...

The asyncio tools in python enable something similar, but very few scripting language debug/tracing tools are as robust as those for JS; that's another area where other languages are often inspired (or aspiring).

Re: The magic of asyncio explained

#66

Post by metalliqaz »

sametmax wrote: post #41
greyman wrote: post #18

Python is my language of first choice, but I must say that I am not that thrilled how this multithreading ended up. There are many tutorials about the topic promising to explain how it works, usually in the form of "simple introduction". But when one tries to implement something production-ready, with correct error handling etc., things starts to complicate pretty quickly; at least that was my experience. I don't wan…

That's because most of those tutorials have not been written by somebody actually putting something in production. I've been using asyncio for a while now, and you can't get away with a short introduction since: - it's very low level - it's full of design flaws and already has accumulated technical debt - it requires very specific best practices to be usable I'm not going to write a tutorial here, it would take me a…

I wish I could favorite comments on HN

Re: The magic of asyncio explained

#67

Post by protonfish »

sadgit wrote: post #3

I’m still bummed that Python took this direction. Maybe introducing new keywords into the language for event loop concurrency was Python’s way of satisfying “explicit is better than implicit” but i can’s shake the feeling that callback passing and generator coroutines are a fad that is complex enough to occupy the imagination of a generation of programmers while offering little benefit compared to green threads.

I wish they had implemented parallelism based on the actor model. It seems like the perfect high-level abstraction for managing parallel processes. All of the asyncio stuff feels too fine-grained for Python-style development.

Re: The magic of asyncio explained

#69

Post by _Codemonkeyism »

_Codemonkeyism wrote: post #52
icebraining wrote: post #39

Earlier quoted context omitted.

Isn't Haskell somewhat like that, due to being lazy by default?

In Haskell you'd have the type signature everywhere I think, mostly as a monad transformer.

Wow, how could this be voted down without comment. Go away trolls!

Re: The magic of asyncio explained

#70

Post by Sir_Cmpwn »

sametmax wrote: post #45
anilakar wrote: post #30

Yet another asyncio tutorial that shows you to run a few sleep tasks concurrently. Can we finally get one that shows how to do real stuff such like socket programming, wrapping non-async-compatible libraries and separating cpu-intensive blocking tasks to awaitable threads?

> such like socket programming That's one of my biggest pet peeves (and if you see my other comments, you'll notice I have quite a few). To do socket programming in asyncio, you can either use: - protocols, with a nice reusable API and an interface that clearly tells you where to do what. But you can't use "await". You are back to creating futures and attaching callback like 10 years ago. - streams, where you can use…

Have you considered contributing improvements to the documentation, or even the API? Python is an open source project.
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