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On Mon, Mar 25, 2019 at 8:02 PM Guido van Rossum <guido@python.org> wrote:
Given PBP, I wonder if we should just relent and have a configurable flag (off by default) to allow nested loop invocations (both the same loop and a different loop).
Allowing reentrant calls to the same loop is not a good idea IMO. At best, you'll need to carefully ensure that the event loop and task implementations are themselves reentrancy-safe (including the C accelerators and third parties like uvloop?), and then it just invites subtle issues in the applications built on top of it. I don't think there's a good reason to allow or support this (and nest_asyncio should be heavily discouraged). I do, however, think that PBP is a good enough reason to allow opt-in use of multiple event loops nested inside each other (maybe something on the EventLoopPolicy for configuration?). -Ben