列表中 Python 错误中的幻方,但 Numpy 数组中没有

Magic Square in Python error in Lists but not in Numpy arrays

我有这两个版本的程序可以生成奇数阶幻方,

1.使用 numpy 数组:

import numpy as np

N = 5
magic_square = np.zeros((N, N), dtype=int)

n = 1
i, j = 0, N // 2

while n <= N ** 2:
    magic_square[i, j] = n
    n += 1
    newi, newj = (i - 1) % N, (j + 1) % N
    if magic_square[newi, newj]:
        i += 1
    else:
        i, j = newi, newj

print(magic_square)

2。使用列表

N = 5
magic_square = [[0] * N] * N

n = 1
i, j = 0, N // 2

while n <= N ** 2:
    magic_square[i][j] = n
    n += 1
    newi, newj = (i - 1) % N, (j + 1) % N
    if magic_square[newi][newj]:
        i += 1
    else:
        i, j = newi, newj

print(magic_square)

但是使用列表的会给出一个 IndexError: list index out of range for line , magic_square[i][j] = n

np 数组和列表的索引有什么不同吗?

如果是,那么如何更正包含列表的代码?

正如 hpaulj 所说,不要使用 [[0]*N]*N]

>>> l = [[0]*5]*5

[[0, 0, 0, 0, 0], 
 [0, 0, 0, 0, 0], # same as above list
 [0, 0, 0, 0, 0], # same as above list
 [0, 0, 0, 0, 0], # same as above list
 [0, 0, 0, 0, 0]] # same as above list

>>> l[0][0] = 5
[[5, 0, 0, 0, 0],
 [5, 0, 0, 0, 0],
 [5, 0, 0, 0, 0],
 [5, 0, 0, 0, 0],
 [5, 0, 0, 0, 0]]

使用

magic_square = [[0 for i in range(N)] for i in range(N)]