Python tricks: Demystifying async, await, and asyncio

[@cakeray]

This is one of the best asyncio explanations if come across so far. Kudos!

[@ondskabenselv]

This is _the best_ asyncio tutorial I've yet encountered. Succinct while not dumming the explanations down!

[@jimmy2643]

This is by far the best simplistic explanation i've seen! Major props and thank you for the video.

[@victortarnovskiy8407]

Probably the clearest example of all I saw trying to figure out the way async/await works. Combined with some theory from PyCon presenters (on matters like "what is event loop for") this one completes the puzzle. Thank you so much for your efforts!

[@anumsheraz4625]

man who are you ? why I didn't knew you before ! Never seen such way of explanation in the way you did. AMAZING, Thank you !

[@Dtomper]

You are sooooooo underrated man, I don't know what's wrong with the KZbin algorithm not showing your videos to people....

[@shopifyexplained]

You know yours is by far the best explaination of Async I have seen on the internet over the past two days trying to learn how async works.

[@Covalent5]

Your teaching capabilities are beyond everything i've encountered.

[@abhijeetkislay8920]

You sir have cleared such deep rooted doubts that I had for parallelism in Python for years and years! Thanks a lot!

[@cetrusbr]

This video is certainly the most helpful about this subject by far

[@Lorant1984]

Oh man, thanks for that. I am yet to understand the details yet, but after watching your video I understood the "concept" of asynchrony and the role of the event loop. GREAT explanation!

[@thabangtsajoa716]

I have tried reading around async all over KZbin, even if you were a IT teacher at junior schools, 10 year olds kids would understand you because of how you simplify it. Thank you Sebastiaan

[@rongeorgia3937]

First, an excellent presentation and explanation. My sincerest thanks. Second, when I first saw the "talking" head in the corner I was like, "What the...?" But as the video went on it was like I was sitting in a coffee shop looking over his shoulder as he explained what was going on. So, I am sold on this. Great job Sebastiaan.

[@rajeshkab]

I have been trying to understand this concept from past 1 month.. Now I feel much better watching this video.. Thanks Sebastiaan

[@amitbuch]

Loved this short tutorial. You are real guru. Salute.

[@letslearnabout4934]

Very great explanations. Not only I know how to use asyncio, but also how it works. Thanks!

[@alexeysilver3139]

Man, this is the best explanation ever, thank you

[@uhadonejob]

Brilliant explanation. Next level teaching.

[@KhoiThinh]

This is hands down the best explanation about asyncio.

[@JoseRodriguez-go5do]

Great explanation with the live coding, really helps to get the concept, but as you said, I/O operations like network, file access and other stuff that depends on "outside code" is what really makes it shine

[@AlexHerlan]

you did a much better job explaining this compared to the top 4 articles returned by google on the subject. Thank you. I like your gradual approach to implementing it... really helped a lot. I'm a lot more familiar with asynchronous javascript, which this is a bit different from... but I think I like it. I certainly like Python over JavaScript in general.

[@thedaynos]

I agree. I have been banging my head against my desk the past few days trying to figure this out from the garbage google links. Just watching this on break at work and i think I can figure out the issue I'm dealing with tonight no problem. thank you!

[@davidegrandis3716]

Totally agreed, by far the best explanation

[@antonyspiano2403]

Thanks brother! can't find anything simple than this in terms of explanation basic concepts. Crystal clear, Thank you!

[@ashukarappa]

Awesome explanation. This was a really great video explaining the concept clearly and in a step by step thought process manner!! Really loved the video. Great job!

[@Thompsonnumber4]

Clear and concise, easy to follow. Excellent!

[@jamtart22]

In case anyone is interested - to determine if a number is prime you only need to check if it has a prime factor smaller than or equal to its square root. Because C=AB must have factor A

[@yahya_abou_imran]

I would like to thank you because it is very difficult to find such a simple example on the net at this time... At the same time, to teach how to make your code async incrementally is just wonderfull. Amazing video! Highly recommended for beginners in async stuff like me!

[@RulerOfCakes]

The best explanation I've come by so far. Thank you so much for this video.

[@MuhammedBasil]

Very comprehensive... Very well explained. Thanks mate.

[@AmitTiwari-sb3qy]

Sebastain, Great Video, I have one doubt, what if => await asyncio.sleep() is not used inside asyc code. Right now I am dealing with some async code. Here code is using async because we have to wait to get some json data from server but I have not seen anywhere , we have used something like await asyncio.sleep(). So does our code is fully asynchronous or do we get benefit by introducing await asyncio.sleep() in our async code

[@alexandrutoma9187]

This is the best coroutines tutorial on the internet.

[@saitaro]

These glasses are fundamental, mate. Thanks for the lesson. btw, could you please explain the practical difference between async, threading, processes etc.?

Thanks! The difference between threading, multiprocessing, and async is a video on its own, but here's the quick summary: With *multiprocessing you* simply start your program twice; so you have two separate instances, each with their own variables, etc. As you can image, communication between processes is difficult. With *threading*, you start two threads of code that run in parallel within a single process (so they share variables, et.c). Unlike with async, the operating system decides which thread runs when. And *async*, as explained here, is in a sense a way to simulate threading in a more controlled way that gives you (almost) complete control over how functions suspend and resume.

[@UniBreakfast]

Any real life examples when this is applicable?

+Михаил Нинин the stereotypical use case would be network communication, in which you often need to wait for data to come in. But I've used coroutines also to implement asynchronous display control and collection of keyboard input.

[@lawrencedoliveiro9104]

Any situation where you need to do multiple things at once, but your code is not CPU bound. In such a situation, threads buy you nothing but complications, whereas coroutines are much simpler to deal with.

[@AlibekAydarov]

kzbin.info/www/bejne/b6vMn42jepiCnc0 - watch this, very good explanation of their core differences

[@admin202]

explanation skills at peak

[@ingenzivany6566]

The best aSYNCIO explanation video thank you.

[@ripperx444]

Finally i understand this better now. People need to do what you did which is explain why you use the keywords and how that works!

Glad you found it useful!

[@lawrencedoliveiro9104]

Note that asyncio is not just a standard Python event loop, it is the standard Python event loop API. There are already plenty of event loops around--in particular, every GUI toolkit already provides one. Rather than try to force everybody to adopt the asyncio event loop (which would never work anyway), what you need to do is wrap these other event loops in an asyncio-compatible layer. Then it becomes possible to write “event-loop-agnostic” code, which is something I don’t think any language has achieved before. For example, GTK has its own event loop, provided by GLib. Here github.com/ldo/glibcoro is an asyncio-compatible wrapper for it, implemented in a little over 400 lines of code. This makes it possible to use the GLib event loop interchangeably with the default asyncio one in non-GUI apps. In GUI apps that are built on GTK, it becomes possible to use Python coroutines to run large parts of the application logic, instead of the more usual event callbacks. Both scenarios are demonstrated here: github.com/ldo/glibcoro_examples

[@zhaofengzheng2923]

You are the coolest programmer I have seen :)

[@kenrosenberg8835]

This tutorial is so on point, the best one on python asyncio

[@yandelyano]

Subscribed shortly after the video started.

[@Jagnathbaba]

very good explanation. One thing I wanted to ask. The time that you give in asyncio.wait function, is that even useful? I mean, we know that it's a point where the function is suspended and another functions might be called. But once another function is called, we cannot really be sure that the function will suspend and get back to the original function in the specified time?

[@donha475]

That was brilliant! The best explanation I've seen! Well done mate! ;)

[@99icd]

Top ! a very clear explanation. Well done and thank you.

[@qipress9552]

I am trying to wrap my head around async/await, threading and multiprocessing in Python. This demo and some of your statements you made were very helpful. I need a few clarifications: 1) For the example that was discussed, because there was an asynchronous sleep, while that was "in progress", it gave up control to the underlying event loop, which in turn switched to the next call, which after doing some quick CPU load (of running the loop) again went to asynchronous sleep, and so on. This meant that "most" of the time, all three sleeps were in progress simultaneously, thus giving the illusion of parallelism. If instead of the asynchronous sleep, if I chose to run a compute intensive calculation (like increment i to a billion), that would be blocking, and would no longer be async, correct? 2) So the await HAS to be on a load that is OUTSIDE the CPU - sleep, network, read disk, etc., correct? 3) Is there a way for me to write my own code which can simulate an async load outside the current thread/process? Like I really do want to increment from 1 to a large number then return, but should happen parallely over multiple coroutines (if that is the right word). Maybe call an external Python script which does that (which will be another process perhaps, I am not sure).

[@waelsadek81]

Thanks for the video well explained. For the is_prime function you can do the division check to and including the square root only no need to go past that.

[@MuhammedBasil]

@Sebastiaan if we move `await asyncio.sleep(0.01)` above the for loop, loop execution will be happen asynchronously, right ? async def highest_prime_below(x): print('Highest prime below %d' % x) await asyncio.sleep(0.01) for y in range(x-1, 0, -1): if is_prime(y): print('→ Highest prime below %d is %d' % (x, y)) return y return None

[@girishsancheti9523]

Very well explained!! Hats Off :)

[@VIKASHKUMAR-kx6vy]

Watched two times And now I think I understand it well.

[@jurajnajiva]

Lets say the function return values need to be passed to the subsequent functions. Would it be possible to make them parallel too?

[@AnimeshPaul23]

Amazing explanation. Thank you Sir. :)

[@toastrecon]

Awesome. Thanks for posting this. The example was great.

[@abdallahabdillah8477]

i don't know why people would dislike this video!!

[@asadraja377]

Very informative and beautifully presented. Thank you so much!

[@fleecky7011]

Hele duidelijke tutorial, dankjewel!

Graag gedaan!

[@codebasics]

Very well explained, love your explanation using code :)

[@gennadyplyushchev1465]

Finally understandable explanation! Thank you!

[@Nakameguro97]

Excellent! Explains why I can't use requests directly in code with coroutines (they block). Subscribing.

[@andreypanin5257]

This was extremely useful and well explained. There's a lot of docs on this subject, but none of them tell how the transition of execution to the loop occurs. Or maybe it's just me who couldn't understand?

[@Mankind5490]

You're the hero we got, but didn't deserve.

[@lawrencedoliveiro9104]

8:00 The asyncio library is pure Python. That means that anything the event loop can do, your own Python code can do. You can implement your own event loop!

[@МихайлоСвєчкін]

This is a great explanation! Thanks!

[@Regalman]

Nice shades and so clear!

[@finster101]

Excellent video! Very clear and understandable. Thanks for sharing your knowledge.

[@elachichai]

Great video. Why didnt you use async def is_prime ? Overlooked? Does not matter?

[@fredpaik1349]

Great explanation. You got my subscription and like for this video. Thanks Sebastiaan!

[@jorgekleinerman6682]

Excellent explanation!! Congrats and thank you very much!

[@dokwonsuh]

Anyone know how he generates that little arrow in his string? Does it have a function, or is it just for readability?

[@romajain2425]

Hey loved your explanation, but one thing is when there are multiple CPU intensive functions which need to be run in async, even after adding async.sleep , it is still slow. Any explanations/workaround for this?

[@gnsc]

very nice explanation with live coding

[@jayh5992]

Is there still a way to run socket functions with asyncio?

[@shervinledu9440]

one-liner for is_prime function at 5:25 is just so nice ! :D

[@brambeer5591]

Great explanation fellow Dutchman!

[@abhishekguha1931]

Excellent ! Understood very well from your video. Keep on the good work.

[@fygarOnTheRun]

Short and concise. What else do you need? Dank je well!

[@ELHAUKEZ]

Hey Sebastian, what do you think about a follow up video for asyncio with generators for the suspending part. With a great example and the quality of your other videos that'll be a nice ressource. So long, best wishes

[@mohnnishsaravanan]

man ! u r the best ! thanks a lot for this best explanation .

[@AlexBenfica]

The best explanation so far! Nice style!

[@marcioinfoful]

Thanks, Dude! that help me a lot! A really great explanation!

[@JoseGarcia-kq2pg]

Thanks for the great explanation.

[@sksahil4374]

hey it is blocking main thread ...i want to add asyncio.get_event_loop() loop.run_until_complete(main()) print('main thread') but i want to end main thread before ending other process .....i do not want to block main thread thread .. how to do that? with asyncio?

[@ytg6663]

So what it does is context switching , right ?

[@stegallo]

Thanks for the video! Very useful. In your example you call all your functions at the same time. What if you want to call them (assume all of them are independent functions) at different times? Do you still need to have them in the wait list? Like appending them at the time of call?

[@manoskoutoulakis6398]

Best asyncio explanation 👍👍👍👍👍

[@HrachyaArshakyan]

Only human friendly explanation that I able to find over internet

[@yourdadsbestfriend7101]

so underrated! amazing

[@arifbasri4950]

This is a great explanation, thank you for this video and the code

[@adityamathur2093]

This guy is a freakin ROCKSTAR! Keep going man

[@KSBond007]

I really enjoy your videos. How did you get around getting the error 'This event loop is already running'? Thx

[@athulyaaugustine3941]

is asyncio and aiohttp supported on windows??

[@Feronom]

what python version you are running?

[@Feronom]

It doesnt work on my 3.7! the part where you introduce asyncio.wait. still runs syncro. And when its finally full asyncro it spits out the smallest number first then waits for the biggest number to finish before it spits out the medium and high together, and speed is still the same as syncro

[@evgenykuznetsov7490]

this is a great explanation.

[@PasselivreEdicoes]

Okay so when you suspend a function with asyncio.sleep, the event loop takes care of deciding which function will take over next. Can the same function that just got suspended be resumed when you do that?

[@Albert-fe8jx]

Very clear. Excellent. Thank you SM.

[@beckhamwilson2112]

great video thanks also those are some cool glasses

[@RogerValor]

well explained, took it as a refresher. Would be awesome to have advanced look at Future in a follow up.

[@Babs42]

In your example is there any other way to "yield" execution than calling await asyncio.sleep()?

[@DmytroLituiev]

great explanation. can you provide your notebook?

Thanks! And sure, here it is: osf.io/w8u26/

[@bierviltbever]

Now this guy is on my wavelength

[@RazmikPoghosyan]

HI Sebastiaan, thanks for amazing explanation. BTW, I have a way of determining of primariness of number. I would like you to take a look at it. def is_prime(x): return not any (not x % i for i in range(2, int(x ** 0.5)))

[@architkapoor2503]

Had making is_prime function an async given more performance gain?

No, in this case it wouldn't improve performance, because is_prime() has no point at which it is 'waisting time', in the way that highest_prime_below() has (with asyncio.sleep()).

[@architkapoor2503]

Thanks. That helps.

[@chaitanyayeole4111]

How many async functions can I run in asyncio.gather?