Glyph wrote:
On Jan 17, 2012, at 5:03 PM, Mark Shannon wrote:
Lets start controversially: I don't like PEP 380, I think it's a kludge.
Too late; it's already accepted. There's not much point in making
controversial statements about it now.
Why is it too late? Presenting this as a fait accompli does not make it
any better. The PEP mailing list is closed to most people, so what forum
for debate is there?
I think that CPython should have proper coroutines, rather than add
more bits and pieces to generators in an attempt to make them more
like coroutines.
By "proper" coroutines, you mean implicit coroutines (cooperative
threads) rather than explicit coroutines (cooperative generators).
Nothing "implicit" about it.
Python has been going in the "explicit" direction on this question for
a long time. (And, in my opinion, this is the right direction to go,
but that's not really relevant here.)
You can use asymmetric coroutines with a scheduler to provide
cooperative threads if you want, but coroutines not have to be used as
threads.
The key advantages of my coroutine implmentation over PEP 380 are:
1. No syntax change.
2. Code can be used in coroutines without modification.
3. No stack unwinding is required at a yield point.
I think this discussion would be more suitable for python-ideas though,
since you have a long row to hoe here. There's already a PEP -
http://www.python.org/dev/peps/pep-0219/ - apparently deferred and not
rejected, which you may want to revisit.
There are several libraries which can give you cooperative threading
already; I assume you're already aware of greenlet and stackless, but I
didn't see what advantages your proposed implementation provides over
those. I would guess that one of the first things you should address on
python-ideas is why adopting your implementation would be a better idea
than just bundling one of those with the standard library :).
Already been discussed:
http://mail.python.org/pipermail/python-ideas/2011-October/012571.html
All of the objections to coroutines (as I propose) also apply to PEP 380.
The advantage of my implementation over greenlets is portability.
I suspect stackless is actually fairly similar to what I have done,
I haven't checked in detail.
Cheers,
Mark.
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