Python：初始化空嵌套列表时的奇怪列表行为

Question

有人可以解释为什么：

b = 10*[[]]
b[0].append(3)

b 现在是：

[[3], [3], [3], [3], [3], [3], [3], [3], [3], [3]]

但如果我这样做：

b = [[] for _ in range(10)]
b[0].append(3)

b 现在是：

[[3], [], [], [], [], [], [], [], [], []]

还要注意的是

10*[[]] == [[] for [] in range(10)]

返回

True

（在 Python 3.6.1 中测试）

Answer 1

 because:
    >>> b = 10*[[]]
    >>> b[0] is b[1]
    True
    >>> b = [[] for _ in range(10)]
    >>> b[0] is b[1]
    False
    >>>