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gh-88831: In docs for asyncio.create_task, explain why strong references to tasks are needed #93258

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ambv merged 4 commits into from
Jun 7, 2022
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gh-88831: In docs for asyncio.create_task, explain why strong references to tasks are needed #93258

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a1b586d
added explicit information about weak and strong references
agrommek May 26, 2022
5148c77
added code example to keep strong references around
agrommek May 26, 2022
e7bf6f8
📜🤖 Added by blurb_it.
blurb-it[bot] May 26, 2022
98fd62f
Reword the message, remove spurious lambda
ambv Jun 7, 2022
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added code example to keep strong references around
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@agrommek
agrommek committed May 26, 2022
commit 5148c7712904356d5a898940d6c3f677950513d5
18 changes: 17 additions & 1 deletion Doc/library/asyncio-task.rst
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Expand Up @@ -228,7 +228,23 @@ Creating Tasks
Save a reference to the result of this function, to avoid
a task disappearing mid execution. The event loop only keeps
weak references to all task. Without a strong reference, the
task may get garbage-collected at any time.
task may get garbage-collected at any time. If you want to have
"fire-and-forget" background tasks you can do something like this::

# create an empty set to store references to background tasks
background_tasks = set()

# start 10 background tasks
for i in range(10):
task = asyncio.create_task(some_coro(param=i))

# Add task to set. This creates a strong reference.
background_tasks.add(task)

# To prevent accumulation of references to already finished
# tasks, make each task remove its own reference from set after
# completion:
task.add_done_callback(lambda t: background_tasks.discard(t))

.. versionadded:: 3.7

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