[Python-Dev] PEP 492 and types.coroutine

Ethan Furman ethan at stoneleaf.us
Sat May 2 19:04:16 CEST 2015

According to https://www.python.org/dev/peps/pep-0492/#id31:

  The [types.coroutine] function applies CO_COROUTINE flag to
  generator-function's code object, making it return a coroutine

Further down in https://www.python.org/dev/peps/pep-0492/#id32:

   [await] uses the yield from implementation with an extra step of
   validating its argument. await only accepts an awaitable,
   which can be one of:


     - A generator-based coroutine object returned from a generator
       decorated with types.coroutine().

If I'm understanding this correctly, type.coroutine's only purpose is to add
a flag to a generator object so that await will accept it.

This raises the question of why can't await simply accept a generator
object?  There is no code change to the gen obj itself, there is no
behavior change in the gen obj, it's the exact same byte code, only a
flag is different.

types.coroutine feels a lot like unnecessary boiler-plate.


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