Question

我有以下代码：

X = [[[None] * 4] * 2] * 6

for i in range(0, 6):
    X[i][0][0] = i

X

结果给出：

[[[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]]]

这对我来说很奇怪，结果不应该如下吗？

[[[0, None, None, None], [0, None, None, None]],
 [[1, None, None, None], [1, None, None, None]],
 [[2, None, None, None], [2, None, None, None]],
 [[3, None, None, None], [3, None, None, None]],
 [[4, None, None, None], [4, None, None, None]],
 [[5, None, None, None], [5, None, None, None]]]

我在这里想念什么？谢谢！

Answer 1

a = [[]] * 2  # here initiated a list and assigned to a.
id(a[0]) >>> 4509460384
id(a[1]) >>> 4509460384

b = [[] for _ in range(2)]  # here constructing a list and assigning to b.
id(b[0]) >>> 4509626808
id(b[1]) >>> 4509626880

希望这清楚！

python：为多维列表赋值

1 个答案: