Can we make this more memory friendly?

https://www.codecademy.com/paths/computer-science/tracks/cspath-discrete-math/modules/counting-theory/lessons/counting-theory-lesson/exercises/applications-of-counting-theory

import string
lower_list = list(string.ascii_lowercase)
upper_list = list(string.ascii_uppercase)
number_list = list(range(0,10))

The lesson has us iterate over each of the above objects. All well and good. My question is, why do we need to cast them to a list when they are already iterable?