asyncio.CancelledError: Task Was Cancelled

Why This Happens

When you call task.cancel(), the task receives CancelledError at the next await point. Catch it for cleanup (closing connections, saving state), but re-raise to complete cancellation.

The Problem

async def worker():
    while True:
        await asyncio.sleep(1)
        print('working')

task = asyncio.create_task(worker())
task.cancel()
await task  # Raises CancelledError

The Fix

async def worker():
    try:
        while True:
            await asyncio.sleep(1)
    except asyncio.CancelledError:
        print('Cleaning up...')
        raise

task = asyncio.create_task(worker())
task.cancel()
try:
    await task
except asyncio.CancelledError:
    print('Task cancelled')

Step-by-Step Fix

1. 1

   Catch for cleanup

   Use try/except asyncio.CancelledError for cleanup.

2. 2

   Always re-raise

   After cleanup, re-raise CancelledError.

3. 3

   Handle at caller

   Wrap await task in try/except at the call site.