Asyncio events

Mar 25, 2024 ยท 2 min read

Asyncio is a powerful feature in Python that allows you to write asynchronous, non-blocking code. This means your program can perform multiple tasks concurrently without getting blocked.

The key concept in asyncio is the event loop. This is like a central hub that manages all the asynchronous tasks. Here's a quick example:

import asyncio

async def my_task(x):
    print(f'Processing {x}')
    await asyncio.sleep(1)
    print(f'Done with {x}')

async def main():
    await asyncio.gather(

This schedules three instances of my_task() to run concurrently. While one task is waiting on the asyncio.sleep(), the event loop can switch to another ready task.

The key things that enable this asynchronous behavior are:

  • The async/await syntax - this marks a function as a coroutine that can be awaited
  • Coroutine functions like asyncio.sleep() that yield control back to the event loop
  • which runs the event loop
  • Practical Examples

    Asyncio works great for I/O bound use cases like:

  • Web scraping - await responses instead of blocking on requests
  • Network programming - handle many concurrent connections
  • Database access - await queries instead of waiting idly
  • It doesn't help much for CPU heavy tasks since there is still a single thread.


    Some challenges with async code:

  • Increased complexity from non-linear program flow
  • Race conditions and bugs from shared mutable state
  • Care required for clean shutdowns
  • Overall asyncio enables more responsive programs. With some care around design, it's a valuable tool for building high performance Python applications.

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