Stefan Behnel, 05.03.2012 15:26:
Vitja Makarov, 27.06.2011 22:31:
2011/6/27 Stefan Behnel:
PEP 380 ("yield from") recently went through the approval gate.
http://www.python.org/dev/peps/pep-0380/
The implementation in CPython isn't rounded up yet and lots of tests are missing from the test suite. But it's agreed that it'll make it into 3.3, and we should try to support it as well. It's a really nice feature.
Wow! Interesting thing. I think that could be implemented but I think we should try to optimize cython generators first.
Coming back to this, the way it's now implemented in CPython is using a new field "f_yieldfrom" in the frame that the coroutine implementation automatically delegates to. Cython's coroutine implementation could do the same thing, and even copy much of the original implementation, by adding a new field to the coroutine class and updating the send(), throw() and close() methods accordingly. The interesting changes are those in Objects/genobject.c and Python/ceval.c in this patch:
http://bugs.python.org/file24214/f8349cbc1b26.diff
That makes it look like most of the work is done for us already.
Just to report some progress here: I got the implementation almost done and it even seems to be quite portable (StopIteration propagates a return value now, but that also works in older Pythons so far). There are a couple of bugs that I'll have to look into, but I should have something ready in a couple of days (or nights...). The CPython tests proved to be quite helpful, but I'll need the usual Cython specific tests as well. If anyone wants to write up some code that you think should work with "yield from" in Cython, I'll happily take it. One additional feature that would be really cool is support for delegating to C arrays and C++ iterators, so that you could wrap C++ iterators with simple values in straight code like this: def gen(): yield from some_cpp_iterable Anyway, that's pretty far off for now as it requires specialised code for the different C/C++ source types. Stefan