generator functions: why won't this work?
Steve Holden
steve at holdenweb.com
Tue Apr 1 23:19:48 EDT 2008
zillow20 at googlemail.com wrote:
> Hi all,
>
> 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 :)
>
In your recursive call you are passing a single argument, a tuple. You
should create it to multiple arguments with a star. Neither do you do
anything with the iterator after you create it.
Try (untested)
####################################
def getNextScalar(*args):
for arg in args:
if ( isinstance(arg, tuple)):
for a in getNextScalar(*arg):
yield a
else:
yield arg
####################################
regards
Steve
--
Steve Holden +1 571 484 6266 +1 800 494 3119
Holden Web LLC http://www.holdenweb.com/
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