yes so if you have async/await all internal, are you saying you can make that work for synchronous code *without* running the event loop?  that is, some kind of container that just does the right thing?  my concern with that would still be performance.    When asyncio was based on yield and exception throws, that was a lot of overhead to add to functions and that was what my performance testing some years back showed.   w/ async/await I'm sure things have been optimized, but in general when i have function a() -> b() -> c(), I am trying to iron as much Python overhead as I possibly can out of that and I'd be concerned that the machinery to work through async/await would add latency.   additionally if it was async/await internally but then i need to access the majority of Python DBAPIs that are sync, I need a thread pool anyway, right?  which is also another big barrier to jump over.

It seems you were involved with urllib3's approach to use a code rewriter rather than a runtime approach based on the discussion at https://github.com/urllib3/urllib3/issues/1323 , but it's not clear if Python 2 compatibility was the only factor or if the concern of "writing a giant shim" was also.