Async Programming with asyncio

The Evolution of Concurrency

Python's asyncio module is the modern way to write concurrent code using the async/await syntax. It's particularly powerful for network-bound tasks.

Core Concepts

Coroutine: A special function that can pause its execution.
Event Loop: Orchestrates the execution of coroutines.
Task: A scheduled coroutine.

Simple Coroutine

import asyncio

async def say_hello():
    print("Hello...")
    await asyncio.sleep(1)
    print("...World!")

asyncio.run(say_hello())

Concurrent Execution

async def main():
    # Run multiple coroutines at once
    await asyncio.gather(
        say_hello(),
        say_hello(),
        say_hello()
    )

asyncio.run(main())

Async Context Managers

Use async with for resources like database connections and HTTP sessions.

import aiohttp

async def fetch_page(url):
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            return await response.text()

✅ Practice (30 minutes)

Write an async function that mimics a long-running database query using asyncio.sleep.
Create a script that fetches data from 10 different URLs concurrently.
Handle timeouts in your async requests using asyncio.wait_for.
Understand the difference between asyncio.create_task and await.