Asyncio event loop

Mar 25, 2024 ยท 2 min read

The asyncio module is one of Python's most powerful tools for writing concurrent and asynchronous code. At the heart of asyncio is the event loop - a central execution unit that manages and schedules all your asynchronous tasks and callbacks.

Here's a quick overview of how the asyncio event loop works:

import asyncio

async def my_async_func():
    print('Hello from async function!')

loop = asyncio.get_event_loop()

When you call asyncio.get_event_loop(), it creates an event loop instance for you. We schedule our my_async_func coroutine to run on this loop by passing it to loop.run_until_complete(). Behind the scenes, the event loop:

  • Monitors tasks and callbacks scheduled to run
  • Waits for I/O operations to complete
  • Decides which task to run next and resumes/pauses execution appropriately
  • This allows you to write asynchronous, non-blocking code like making multiple web requests in parallel without worrying about low-level threading or synchronization issues.

    Tip: Use the async/await syntax to define coroutines that can be scheduled on the event loop:

    async def my_coro():
        await some_web_request() 

    Challenge: The event loop runs in a single thread. So while your coroutines themselves are non-blocking, they cannot take advantage of multiple CPUs. Solutions like asyncio.run_in_executor() can help.

    In summary, mastering asyncio event loop allows you to write highly efficient asynchronous code to deal with scenarios like handling thousands of concurrent requests. Make sure to structure your code properly into separate coroutines and tasks to get the most out of it.

    Browse by tags:

    Browse by language:

    The easiest way to do Web Scraping

    Get HTML from any page with a simple API call. We handle proxy rotation, browser identities, automatic retries, CAPTCHAs, JavaScript rendering, etc automatically for you

    Try ProxiesAPI for free

    curl ""

    <!doctype html>
        <title>Example Domain</title>
        <meta charset="utf-8" />
        <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />


    Don't leave just yet!

    Enter your email below to claim your free API key: