lst = [1, 2, 3]
lst[1] = "????"
print(lst)

s = "abc"
#s[1] = "z" # error!

###

x = [1, 2, 3]
y = x
y.append(4)
print("x:", x)
print("y:", y)

###

def destructiveDouble(lst):
    for i in range(len(lst)):
        lst[i] = lst[i] * 2

a = [1, 2, 3]
b = destructiveDouble(a)
print("a:", a)
print("b:", b)

###

def nonDestructiveDouble(lst):
    result = []
    for i in range(len(lst)):
        result.append(lst[i] * 2)
    return result

a = [1, 2, 3]
b = nonDestructiveDouble(a)
print("a:", a)
print("b:", b)