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

[Guido van Rossum]

On Tue, Mar 24, 2009 at 8:35 PM, P.J. Eby <pje at telecommunity.com> 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', and
> then having what seem like mysterious off-by-one errors, or being confused
> by receiving a generator object instead of their desired non-generator
> return value.
>
> 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!
>
> But if it were spelled 'raise Return(value)' or 'raise StopIteration(value)'
> or something similar (or even had its own syntax!), I wouldn't object, as it
> would then be obvious how to get the value, and there could be no possible
> confusion with a regular return value.
>
> 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.

I'm sympathetic to this point of view.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)