Question

In the examples below, resp.results is an iterator.

Version1 :

items = []
for result in resp.results:
     item = process(result)
     items.append(item)
return iter(items)

Version 2:

for result in resp.results:
     yield process(result)

Is returning iter(items) in Version 1 any better/worse in terms of performance/memory savings than simply returning items?

In the “Python Cookbook,” Alex says the explicit iter() is “more flexible but less often used,” but what are the pros/cons of returning iter(items) vs yield as in Version 2?

Also, what are the best ways to unittest an iterator and/or yield? — you can’t do len(results) to check the size of the list?

Answer 1

It’s easy to turn an iterator or generator back into a list if you need it:

results = [item for item in iterator]

Or as kindly pointed out in the comments, an even simpler method:

results = list(iterator)