Variable assignment and change - Mutable list
b = [5, 6]
a = b # this is a copy of the *reference* only
# if we change the list in a, it will
# change the list connected to b as well
print(a) # [5, 6]
print(b) # [5, 6]
a[0] = 1
print(a) # [1, 6]
print(b) # [1, 6]
a = [7, 8] # replace the whole list
print(a) # [7, 8]
print(b) # [1, 6]