[Python-Dev] PEP 380 (yield from a subgenerator) comments (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Fri Mar 27 04:08:07 CET 2009

Antoine Pitrou wrote:

There seems to be a misunderstanding as to how generators are used in Twisted. There isn't a global "trampoline" to schedule generators around. Instead, generators are wrapped with a decorator (*) which collects each yielded value (it's a Deferred object) and attaches to it a callback which resumes (using send()) the execution of the generator whenever the Deferred finally gets its value.

This sounds like an architecture that was developed to work around the lack of anything like yield-from in the language.

You can't expect to improve something like that by stuffing yield-from into the existing framework, because the point of yield-from is to render the framework itself unnecessary. To take full advantage of it, you need to step back and re-design the whole thing in a different way.

In the case of Twisted, I expect the new design would look a lot like my generator scheduling example.

-- Greg

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