导论
首先，举一个例子：
a = [1, 2, 3]
b = (1, 2, 3)
print(id(a)) # To print the identity of a
print(id(b)) # To print the identity of b
a += [4, 5] # a = a + [4, 5]
# That is, a.extend([4, 5])
b += (4, 5)
print(a)
print(b)
print(id(a)) # To print the identity o
