[Python-Dev] PEP 380 (yield from a subgenerator) comments
pje at telecommunity.com
Sat Mar 21 17:25:05 CET 2009
At 04:45 PM 3/21/2009 +1000, Nick Coghlan wrote:
>I really like the PEP - it's a solid extension of the ideas introduced
>by PEP 342.
(Replying to you since I haven't seen any other thread on this)
My concern is that allowing 'return value' in generators is going to
be confusing, since it effectively causes the return value to
"disappear" if you're not using it in this special way with some
framework that takes advantage.
However, if you *do* have some framework that takes advantage of
generators to do microthreads, then it is most likely already written
so as to have things like 'yield Return(value)' to signal a return,
and to handle 'yield subgenerator()' without the use of additional syntax.
So, I don't really see the point of the PEP. 'yield from' seems
marginally useful, but I really dislike making it an expression,
rather than a statement. The difference seems just a little too
subtle, considering how radically different the behavior
is. Overall, it has the feel of jamming a framework into the
language, when doing the same thing in a library is pretty trivial.
I'd almost rather see a standard or "reference" trampoline added to
the stdlib (preferably with a way to register handling for
specialized yielded types IO/scheduling hooks), than try to cram half
a trampoline into the language itself.
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