The drop_last generator takes one iterable and one int as a parameter (call it n): it produces every value from the iterable except for the last n values (without being able to count how many values the iterable produces) hint: i used an explicit call to iter and a while loop and a comprehension that creates a list that stores at most n values (so that data structure is allowed here). for example for i in drop_last('combustible', 5): print(i, end='') prints combus; if the iterable produces < n values, it terminates immediately, on the first call to next.