# separation pf concern # clear and understandable # easy to extend # easy to maintain # memory efficient # DRY # pure function # 1. given the same input and return the same result # 2. produces no side effect def multiply_by_two(li): new_list = [] for i in li: new_list.append(i*2) return new_list print(multiply_by_two([1,2,3])) # if the function returns print() then it is not pure function