[Python-Dev] Re: PEP 255: Simple Generators

[Jeff Epler]

On Tue, Jun 19, 2001 at 06:21:14PM +1200, Greg Ewing wrote:
> Something is bothering me about this. In fact,
> it's bothering me a LOT. In the following, will
> f() work as a generator-function:
> 
>   def f():
>     for i in range(5):
>       g(i)
> 
>   def g(i):
>     for j in range(10):
>       yield i,j
> 
> If I understand PEP255 correctly, this will *not*
> work. But it seems entirely reasonable to me that
> it *should* work. It *has* to work, otherwise how
> am I to write generators that are too complicated
> to fit into a single function?

The following similar code seems to produce the results you have in
mind.

    def f():
        for i in range(5):
            #g(i)
            #yield g(i)
            for x in g(i): yield x

    def g(i):
        for j in range(10):
            yield i, j

It would be nice to have a succinct way to say
'for dummy in iterator: yield dummy'.  Maybe 'yield from iterator'?
Then f would become:
    def f():
        for i in range(5):
            yield from g(i)

Jeff
PS I noticed that the generator branch got merged into the trunk.  Cool!