Why am I getting None after using sort or reverse?

• sort
• reverse
• None

x = [1,2,3]
y = x.sort()
z = x.reverse()
print(y)
print(z)

Expected result:

[1,2,3]
[3,2,1]

Actual result:

None
None

• sort() and reverse() functions do not work
• Why does "return list.sort()" return None, not the list?