Python 3.6+sysfunction

sys.get_asyncgen_hooks()

asynchronous code

Returns the asynchronous generator hooks (firstiter, finalizer) installed by the event loop — to close abandoned async generators.

Syntax

sys.get_asyncgen_hooks()

Outside an event loop both fields are None; inside asyncio.run() asyncio installs them. That is why an async generator abandoned mid async for does not lose its finally: the finalizer hook schedules its aclose() on the event loop, and loop.shutdown_asyncgens() closes any still alive at the end. Application code does not need these hooks — they are for people writing their own event loops.

Examples

import asyncio, sys
print(sys.get_asyncgen_hooks().firstiter)  # → None
async def main():
    hooks = sys.get_asyncgen_hooks()
    print(hooks.firstiter is not None, hooks.finalizer is not None)
asyncio.run(main())  # → True True

See also

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