[Python-Dev] PEP 380 (yield from a subgenerator) comments

[Greg Ewing]

P.J. Eby wrote:

> Now, if somebody came up with a different way to spell the extra value 
> return, I wouldn't object as much to that part.  I can just see people 
> inadvertently writing 'return x' as a shortcut for 'yield x; return', 

Well, they need to be educated not to do that. I'm
not sure they'll need much education about this
anyway. They've already been taught not to say
'return' when they mean 'yield', so I don't see why
they should suddenly start doing so now.

I'd be disappointed to lose that part of the proposal.
Part of my philosophy is that suspendable functions
should have the same rights and privileges as ordinary
ones, and that includes the ability to return values
using 'return'.

> It also seems weird that the only syntactically-supported way to get the 
> generator's "return value" is to access it inside *another* 
> generator...  which *also* can't return the return value to anyone!

Would you be happier if some syntactic way to do that
were provided?

It could perhaps be done by enhancing the part of the
'for' loop that gets executed upon normal termination
of the iterator.

   for x in my_iter:
     do_something_with(x)
   else v:
     handle_return_value(v)

> The unusual spelling would also signal that something unusual (i.e., 
> multitasking) is taking place, similar to the way some frameworks use 
> things like 'yield Return(value)' to signal the end of a task and its 
> return value, in place of a value in the stream.

Difference in philosophy again. To me, the need for such
an unusual construct when using these frameworks is a
wart, not a feature.

-- 
Greg