Interesting little "gotcha" with generators

[Will McGugan]

Kenneth McDonald wrote:
> I recently had need to write the following code:
> 
>     def compileOuter(self):
>         if False: yield None
>         else: return
> 
> "compileOuter" is a generator function which is implemented in  various 
> classes. In this particular class, it always yields nothing.  However, 
> none of the following work:
> 
>     def compileOuter(self):
>         return
> 
>     def compileOuter(self):
>         pass
> 
>     def compileOuter(self):
>         yield
> 
> The first two don't work because in order to define a generator, you  
> must have a yield statement inside it. The last doesn't work because  
> every "yield" must have an argument.
> 
> I've been using "return" in generators ever since I started using  
> generators, but on reflection, it seems to me that such a thing is in  
> some ways inconsistent; "return" is (conceptually, at least  originally) 
> a function statement, where "return" by itself really  stands in for 
> "return None". But in generators, it is being used as a  control flow 
> command. For example, you can't have "return" with an  argument inside a 
> generator.
> 
> Too bad "return" wasn't entirely forbidden within generators, and  
> "yield" without an argument mandated instead. Oh well, too let now I  
> suppose...

Would this work?

def compilerOuter(self):
	raise StopIteration

Will McGugan
-- 
http://www.willmcgugan.com
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