Leaving early and building a list

Sometimes you want to stop the moment you find what you are after. return works in the middle of a loop too: it ends the function there and then. Most tasks with the word "first" are solved this way.

1for i in range(len(values)):
2    if values[i] == key:
3        return i
4return -1

len(values) is the number of elements; range(len(values)) counts from 0 to the last index, so you have both the position (i) and the value (values[i]). If the loop ends and you have not returned, what you wanted is not there.

1out = []
2for v in values:
3    if v % 2 == 0:
4        out.append(v)
5return out

When the answer is a list, start with an empty one ([]) and add the elements that qualify to its end with append. The order keeps itself.

Tasks