Async Programming

async/await lets a program work on other tasks while waiting on something slow (a network request, a database query), instead of sitting idle.

import asyncio

async def fetch_data(id):
    await asyncio.sleep(1)   # simulates a slow network call
    return f"data-{id}"

async def main():
    results = await asyncio.gather(
        fetch_data(1), fetch_data(2), fetch_data(3),
    )
    print(results)

asyncio.run(main())

Expected output

['data-1', 'data-2', 'data-3']

asyncio.gather runs all three fetch_data calls concurrently — the whole program waits about 1 second total, not 3, since they overlap while each is "waiting."

Common mistakes

• Calling an async def function without await — it returns a not-yet-run coroutine object instead of the actual result.