Questions tagged [python-asyncio]

This tag is to be used for the asyncio Python package which provides mechanisms for writing single-threaded concurrent code. The asyncio package provides asynchronous I/O, event loop, coroutines and tasks beginning with Python 3.4.

This module provides infrastructure for writing single-threaded concurrent code using coroutines, multiplexing I/O access over sockets and other resources, running network clients and servers, and other related primitives. Here is a more detailed list of the package contents:

a pluggable event loop with various system-specific implementations;
transport and protocol abstractions (similar to those in Twisted);
concrete support for TCP, UDP, SSL, subprocess pipes, delayed calls, and others (some may be system-dependent);
a Future class that mimicks the one in the concurrent.futures module, but adapted for use with the event loop;
coroutines and tasks based on yield from (PEP 380), to help write concurrent code in a sequential fashion;
cancellation support for Futures and coroutines;
synchronization primitives for use between coroutines in a single thread, mimicking those in the threading module;
an interface for passing work off to a threadpool, for times when you absolutely, positively have to use a library that makes blocking I/O calls.
Recently Python 3.5 introduced async/await for enhancing the module for more readablity instead of yield from.

7214 questions

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How does asyncio actually work?

This question is motivated by my another question: How to await in cdef? There are tons of articles and blog posts on the web about asyncio, but they are all very superficial. I couldn't find any information about how asyncio is actually…

asked Feb 27 '18 at 09:48

wvxvw

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multiprocessing vs multithreading vs asyncio

I found that in Python 3.4, there are few different libraries for multiprocessing/threading: multiprocessing vs threading vs asyncio. But I don't know which one to use or is the "recommended one". Do they do the same thing, or are different? If so,…

python multithreading python-3.x multiprocessing python-asyncio

asked Dec 12 '14 at 01:03

user3654650

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asyncio.gather vs asyncio.wait (vs asyncio.TaskGroup)

asyncio.gather and asyncio.wait seem to have similar uses: I have a bunch of async things that I want to execute/wait for (not necessarily waiting for one to finish before the next one starts). Since Python 3.11 there is yet another similar feature,…

python asynchronous async-await python-asyncio

asked Feb 14 '17 at 16:21

Claude

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Asynchronous method call in Python?

I was wondering if there's any library for asynchronous method calls in Python. It would be great if you could do something like @async def longComputation():




token = longComputation()
token.registerCallback(callback_function)
#…


        
            
                
                python 
                
                asynchronous 
                
                python-asyncio 
                
                coroutine 
                
            
            
                
                    

    asked Aug 06 '09 at 13:55
    
        
    
    
        Stefano Borini
        
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        Simplest async/await example possible in Python
        I've read many examples, blog posts, questions/answers about asyncio / async / await in Python 3.5+, many were complex, the simplest I found was probably this one.
Still it uses ensure_future, and for learning purposes about asynchronous programming…
        
            
                
                python 
                
                python-3.x 
                
                asynchronous 
                
                async-await 
                
                python-asyncio 
                
            
            
                
                    

    asked Jun 08 '18 at 09:28
    
        
    
    
        Basj
        
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        "Fire and forget" python async/await
        Sometimes there is some non-critical asynchronous operation that needs to happen but I don't want to wait for it to complete.  In Tornado's coroutine implementation you can "fire & forget" an asynchronous function by simply ommitting the yield…
        
            
                
                python 
                
                python-3.5 
                
                python-asyncio 
                
            
            
                
                    

    asked May 17 '16 at 14:13
    
        
    
    
        Mike N
        
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        How to set class attribute with await in __init__
        How can I define a class with await in the constructor or class body?
For example what I want:
import asyncio

# some code


class Foo(object):

    async def __init__(self, settings):
        self.settings = settings
        self.pool = await…
        
            
                
                python 
                
                python-3.x 
                
                python-asyncio 
                
            
            
                
                    

    asked Oct 14 '15 at 14:36
    
        
    
    
        uralbash
        
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        RuntimeError: This event loop is already running in python
        I think I'm getting this error because my code calls asyncio.get_event_loop().run_until_complete(foo()) twice.  Once from foo() and second time from function called by foo(). My question is then: why should this be a problem? Why should I even care…
        
            
                
                python 
                
                python-asyncio 
                
            
            
                
                    

    asked Oct 19 '17 at 09:41
    
        
    
    
        wvxvw
        
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        asyncio.ensure_future vs. BaseEventLoop.create_task vs. simple coroutine?
        I've seen several basic Python 3.5 tutorials on asyncio doing the same operation in various flavours.
In this code:
import asyncio  

async def doit(i):
    print("Start %d" % i)
    await asyncio.sleep(3)
    print("End %d" % i)
    return i

if…
        
            
                
                python 
                
                python-3.x 
                
                python-3.5 
                
                coroutine 
                
                python-asyncio 
                
            
            
                
                    

    asked Mar 31 '16 at 20:15
    
        
    
    
        crusaderky
        
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        "asyncio.run() cannot be called from a running event loop" when using Jupyter Notebook
        I would like to use asyncio to get webpage html.
I run the following code in jupyter notebook:
import aiofiles
import aiohttp
from aiohttp import ClientSession

async def get_info(url, session):
    resp = await session.request(method="GET",…
        
            
                
                python 
                
                python-3.x 
                
                jupyter-notebook 
                
                python-asyncio 
                
            
            
                
                    

    asked Mar 29 '19 at 02:24
    
        
    
    
        Chan
        
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        Difference between coroutine and future/task in Python 3.5?
        Let's say we have a dummy function:
async def foo(arg):
    result = await some_remote_call(arg)
    return result.upper()

What's the difference between:
import asyncio    

coros = []
for i in range(5):
    coros.append(foo(i))

loop =…
        
            
                
                python 
                
                python-3.x 
                
                python-asyncio 
                
            
            
                
                    

    asked Jan 12 '16 at 20:43
    
        
    
    
        knite
        
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        How to test Python 3.4 asyncio code?
        What's the best way to write unit tests for code using the Python 3.4 asyncio library? Assume I want to test a TCP client (SocketConnection):
import asyncio
import unittest

class TestSocketConnection(unittest.TestCase):
    def setUp(self):
       …
        
            
                
                python 
                
                unit-testing 
                
                python-3.x 
                
                python-unittest 
                
                python-asyncio 
                
            
            
                
                    

    asked Apr 12 '14 at 17:43
    
        
    
    
        Marvin Killing
        
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        How to limit concurrency with Python asyncio?
        Let's assume we have a bunch of links to download and each of the link may take a different amount of time to download. And I'm allowed to download using utmost 3 connections only. Now, I want to ensure that I do this efficiently using…
        
            
                
                python 
                
                python-3.x 
                
                asynchronous 
                
                concurrency 
                
                python-asyncio 
                
            
            
                
                    

    asked Jan 28 '18 at 05:08
    
        
    
    
        Shridharshan
        
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        What is the core difference between asyncio and trio?
        Today, I found a library named trio which says itself is an asynchronous API for humans. These words are a little similar with requests'. As requests is really a good library, I am wondering what is the advantages of trio.
There aren't many articles…
        
            
                
                python 
                
                asynchronous 
                
                python-asyncio 
                
                python-trio 
                
                curio 
                
            
            
                
                    

    asked Mar 26 '18 at 02:07
    
        
    
    
        Sraw
        
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        RuntimeError: There is no current event loop in thread in async + apscheduler
        I have a async function and need to run in with apscheduller every N minutes.
There is a python code below
URL_LIST = ['',
            '',
            '',
            ]

def demo_async(urls):
    """Fetch list of web pages…
        
            
                
                python 
                
                python-3.x 
                
                python-asyncio 
                
                aiohttp 
                
                apscheduler 
                
            
            
                
                    

    asked Oct 13 '17 at 10:27
    
        
    
    
        Valera Shutylev
        
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