How (in)efficient is a list comprehension if you don't assign it?

Question

In this question, I\'m having an argument with a commenter who argues that

for t in threads:
    t.join()

would be better than

Answer 1

If you want a one-liner for this, write an exhaust function, and use it in conjunction with a generator expression:

def exhaust(iterator):
    for _ in iterator:
        pass

exhaust(t.join() for t in threads)

Then you aren't paying the cost for all of the list storage.

Feel free to rename exhaust something more snappy or relevant to your usage.

I've seen this list-comprehension abuse quite a lot, even in interview coding samples where we've explicitly instructed candidates to avoid unbounded memory growth when solving the problem.