itertools.flatten()? and copying generators/iterators.

[Peter Otten]

Francis Avila wrote:

>> for flatten_dict(). So you get some speed up at the cost of uglier though
>> still quite readable code and under the assumption that either all or no
>> instances of a class are iterable.
> 
> That's not always a good assumption to make, if we want to decide whether
> to iterate based upon some property of the object (which is actually how I
> originally discovered I needed a "flatten").
> 
> Perhaps we can combine both conditions and caching optimizations?

I didn't work this out, but I suppose the way to go is to allow three states
(ALWAYS, NEVER, NOCACHE) in the dictionary and only invoke itercond() on
cache misses and NOCACHE values.

Peter