def double_list(x):
    i = 0
    while i < len(x):
        x[i] *= 2
        i += 1


a = [1, 2, 3, 4, 5]
double_list(a)
print(a)


print("\n\n")


def double_list(x):
    r = []
    for i in x:
        r.append(i * 2)
    return r


a = [1, 2, 3, 4, 5]
a = double_list(a)
print(a)