async / await

A model for code that waits: network I/O, timers, queues. While one coroutine is waiting, the event loop runs another.

Three keywords

• async def — defines a coroutine (a function that returns a coroutine object)
• await x — pause this coroutine until x completes
• asyncio.gather(*coros) — run many coroutines concurrently and wait for all

In Pyodide

The browser's event loop is asyncio's event loop. await at the top level Just Works.

Common pitfall

Calling async_fn() without await returns a coroutine object — it does not run. Always await or pass to gather.

Try it

1. Convert the three fetch_thing calls to run sequentially with await — observe the time difference.
2. Use asyncio.create_task and check the difference vs gather.