generator functions: why won't this work?

[Mel]

zillow20 at googlemail.com wrote:
> I'm trying to understand generator functions and the yield keyword.
> I'd like to understand why the following code isn't supposed to work.
> (What I would have expected it to do is, for a variable number of
> arguments composed of numbers, tuples of numbers, tuples of tuples,
> etc., the function would give me the next number "in sequence")
> ####################################
> def getNextScalar(*args):
>    for arg in args:
>       if ( isinstance(arg, tuple)):
>          getNextScalar(arg)
>       else:
>          yield arg
> ####################################
> 
> # here's an example that uses this function:
> # creating a generator object:
> g = getNextScalar(1, 2, (3,4))
> g.next() # OK: returns 1
> g.next() # OK: returns 2
> g.next() # not OK: throws StopIteration error
> 
> ####################################
> 
> I'm sure I'm making some unwarranted assumption somewhere, but I
> haven't been able to figure it out yet (just started learning Python a
> couple of days ago).
> 
> Any help will be appreciated :)

`getNextScalar(arg)` doesn't yield anything (it creates, but doesn't 
use, a new generator object,) so nothing comes out.  Look at

 >>> h = getNextScalar(1,2,(3,4),5)
 >>> h.next()
1
 >>> h.next()
2
 >>> h.next()
5


Maybe you want

     if isinstance (arg, tuple):
         for s in getNextScalar (*arg):
             yield s




	Mel.