list中加等于和extend以及append的区别

a = [1,2]

a += [3,4]

print(a)

输出：[1, 2, 3, 4]

a = [1,2]

a.extend([3,4])

print(a)

输出：
[1, 2, 3, 4]

a = [1,2]

a.append([3,4])

print(a)

输出：[1, 2, [3, 4]]