In the previous post, we had the following code:

python
import asyncio

async def child():
...

async def main():
asyncio.create_task(child())
...

Can you spot a bug?

Since we don't store a reference to the background task we create, the garbage collector may destroy the task before it finishes. To avoid that, we need to store a reference to the task until it finishes. The official documentation recommends the following pattern:

python
bg_tasks = set()

async def main():
t = asyncio.create_task(child())

# hold the reference to the task
# in a global set
bg_tasks.add(t)

# automatically remove the task
# from the set when it's done
t.add_done_callback(bg_tasks.discard)

...

Python etc

In the previous post, we had the following code:

python
import asyncio

async def child():
...

async def main():
asyncio.create_task(child())
...

Can you spot a bug?

Since we don't store a reference to the background task we create, the garbage collector may destroy the task before it finishes. To avoid that, we need to store a reference to the task until it finishes. The official documentation recommends the following pattern:

python
bg_tasks = set()

async def main():
t = asyncio.create_task(child())

# hold the reference to the task
# in a global set
bg_tasks.add(t)

# automatically remove the task
# from the set when it's done
t.add_done_callback(bg_tasks.discard)

...

hottg.com/pythonetc/725

7.6K viewsedited  Apr 25, 2023 at 14:01