python: FOR 循环，迭代赋值未分配正确的值

Question

我正在制作一个列表，其中嵌套了一个列表。我需要遍历第二个列表，并为位置分配一个值。所以我写了这个

matrix=[]
list=[0,1,2,3,4,5,6,7,8,9]
def board():
    for x in range(10):
        for y in range(10):
            matrix.append([[x,y],1]) #A grid is made, with a spare element
    for i in range(100):
        matrix[i][1]=list            #The grid is two elements, co-ords...
                                     #and a list of attributes


board()
for i in range(100):
    matrix[i][2][0]=i        #The first attribute,(in 2nd of2elements),
print(matrix)                ##SHOULD be its own position

此代码的所有变体都会产生相同的结果：

Error or the number "99" being placed in EVERY INSTANCE of that location. That is to say my final FOR loop seems to be assigning "99" NOT i...

我已经尝试了几个变体（在 FOR 循环内生成数字是我的偏好，唉）我花了大约 6 个小时盯着这个看。我所有的逻辑都告诉我，计算机应该知道我想要第二个元素的第一个元素是计数 0,1,2... 我知道这不可能是因为语言限制，所以请告诉我我没有看到的内容。

Answer 1

matrix[i][1]=list

执行此操作时，相同的数组被分配到矩阵数组中。因此，如果您更改一项，则所有项都会更改。而是像这样分配列表的副本：

matrix[i][1] = list[:]

正如@Bakuriu 所指出的，在 python 3 中你可以使用 list.copy() 方法。在 Python 2 中，您可以使用 copy 模块来复制带有 l2 = copy.copy(l1)

的容器

此外，您应该更改变量 'list' 的名称，因为 'list' 是 python 中的内置类型。

Answer 2

您应该替换 matrix[i][2][0]=i 赋值，因为它会引发 IndexError 到：

for i in range(100):
    matrix[i][1][0]=i        #The first attribute,(in 2nd of2elements),
print(matrix)                ##SHOULD be its own position

Answer 3

列表在 for 循环中更快，但这里你有字典的解决方案：

from pprint import pprint as ppr

matrix={}
list=[0,1,2,3,4,5,6,7,8,9]
def board():
    for x in range(10):
        for y in range(10):
            matrix[(x,y)]=1 
    for k in matrix.keys():
        matrix[k]=list

board()
ppr(matrix)

for k in matrix.iterkeys():
    v=matrix[k][:]   
    v[2]=k[0]*10+k[1]
    matrix[k]=v
ppr(matrix)

输入：

{(0, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (1, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (2, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (3, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (4, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (5, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (6, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (7, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (8, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 0): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 1): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 3): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 4): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 5): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 6): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 7): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 8): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (9, 9): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]}

输出：

{(0, 0): [0, 1, 0, 3, 4, 5, 6, 7, 8, 9],
 (0, 1): [0, 1, 1, 3, 4, 5, 6, 7, 8, 9],
 (0, 2): [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 (0, 3): [0, 1, 3, 3, 4, 5, 6, 7, 8, 9],
 (0, 4): [0, 1, 4, 3, 4, 5, 6, 7, 8, 9],
 (0, 5): [0, 1, 5, 3, 4, 5, 6, 7, 8, 9],
 (0, 6): [0, 1, 6, 3, 4, 5, 6, 7, 8, 9],
 (0, 7): [0, 1, 7, 3, 4, 5, 6, 7, 8, 9],
 (0, 8): [0, 1, 8, 3, 4, 5, 6, 7, 8, 9],
 (0, 9): [0, 1, 9, 3, 4, 5, 6, 7, 8, 9],
 (1, 0): [0, 1, 10, 3, 4, 5, 6, 7, 8, 9],
 (1, 1): [0, 1, 11, 3, 4, 5, 6, 7, 8, 9],
 (1, 2): [0, 1, 12, 3, 4, 5, 6, 7, 8, 9],
 (1, 3): [0, 1, 13, 3, 4, 5, 6, 7, 8, 9],
 (1, 4): [0, 1, 14, 3, 4, 5, 6, 7, 8, 9],
 (1, 5): [0, 1, 15, 3, 4, 5, 6, 7, 8, 9],
 (1, 6): [0, 1, 16, 3, 4, 5, 6, 7, 8, 9],
 (1, 7): [0, 1, 17, 3, 4, 5, 6, 7, 8, 9],
 (1, 8): [0, 1, 18, 3, 4, 5, 6, 7, 8, 9],
 (1, 9): [0, 1, 19, 3, 4, 5, 6, 7, 8, 9],
 (2, 0): [0, 1, 20, 3, 4, 5, 6, 7, 8, 9],
 (2, 1): [0, 1, 21, 3, 4, 5, 6, 7, 8, 9],
 (2, 2): [0, 1, 22, 3, 4, 5, 6, 7, 8, 9],
 (2, 3): [0, 1, 23, 3, 4, 5, 6, 7, 8, 9],
 (2, 4): [0, 1, 24, 3, 4, 5, 6, 7, 8, 9],
 (2, 5): [0, 1, 25, 3, 4, 5, 6, 7, 8, 9],
 (2, 6): [0, 1, 26, 3, 4, 5, 6, 7, 8, 9],
 (2, 7): [0, 1, 27, 3, 4, 5, 6, 7, 8, 9],
 (2, 8): [0, 1, 28, 3, 4, 5, 6, 7, 8, 9],
 (2, 9): [0, 1, 29, 3, 4, 5, 6, 7, 8, 9],
 (3, 0): [0, 1, 30, 3, 4, 5, 6, 7, 8, 9],
 (3, 1): [0, 1, 31, 3, 4, 5, 6, 7, 8, 9],
 (3, 2): [0, 1, 32, 3, 4, 5, 6, 7, 8, 9],
 (3, 3): [0, 1, 33, 3, 4, 5, 6, 7, 8, 9],
 (3, 4): [0, 1, 34, 3, 4, 5, 6, 7, 8, 9],
 (3, 5): [0, 1, 35, 3, 4, 5, 6, 7, 8, 9],
 (3, 6): [0, 1, 36, 3, 4, 5, 6, 7, 8, 9],
 (3, 7): [0, 1, 37, 3, 4, 5, 6, 7, 8, 9],
 (3, 8): [0, 1, 38, 3, 4, 5, 6, 7, 8, 9],
 (3, 9): [0, 1, 39, 3, 4, 5, 6, 7, 8, 9],
 (4, 0): [0, 1, 40, 3, 4, 5, 6, 7, 8, 9],
 (4, 1): [0, 1, 41, 3, 4, 5, 6, 7, 8, 9],
 (4, 2): [0, 1, 42, 3, 4, 5, 6, 7, 8, 9],
 (4, 3): [0, 1, 43, 3, 4, 5, 6, 7, 8, 9],
 (4, 4): [0, 1, 44, 3, 4, 5, 6, 7, 8, 9],
 (4, 5): [0, 1, 45, 3, 4, 5, 6, 7, 8, 9],
 (4, 6): [0, 1, 46, 3, 4, 5, 6, 7, 8, 9],
 (4, 7): [0, 1, 47, 3, 4, 5, 6, 7, 8, 9],
 (4, 8): [0, 1, 48, 3, 4, 5, 6, 7, 8, 9],
 (4, 9): [0, 1, 49, 3, 4, 5, 6, 7, 8, 9],
 (5, 0): [0, 1, 50, 3, 4, 5, 6, 7, 8, 9],
 (5, 1): [0, 1, 51, 3, 4, 5, 6, 7, 8, 9],
 (5, 2): [0, 1, 52, 3, 4, 5, 6, 7, 8, 9],
 (5, 3): [0, 1, 53, 3, 4, 5, 6, 7, 8, 9],
 (5, 4): [0, 1, 54, 3, 4, 5, 6, 7, 8, 9],
 (5, 5): [0, 1, 55, 3, 4, 5, 6, 7, 8, 9],
 (5, 6): [0, 1, 56, 3, 4, 5, 6, 7, 8, 9],
 (5, 7): [0, 1, 57, 3, 4, 5, 6, 7, 8, 9],
 (5, 8): [0, 1, 58, 3, 4, 5, 6, 7, 8, 9],
 (5, 9): [0, 1, 59, 3, 4, 5, 6, 7, 8, 9],
 (6, 0): [0, 1, 60, 3, 4, 5, 6, 7, 8, 9],
 (6, 1): [0, 1, 61, 3, 4, 5, 6, 7, 8, 9],
 (6, 2): [0, 1, 62, 3, 4, 5, 6, 7, 8, 9],
 (6, 3): [0, 1, 63, 3, 4, 5, 6, 7, 8, 9],
 (6, 4): [0, 1, 64, 3, 4, 5, 6, 7, 8, 9],
 (6, 5): [0, 1, 65, 3, 4, 5, 6, 7, 8, 9],
 (6, 6): [0, 1, 66, 3, 4, 5, 6, 7, 8, 9],
 (6, 7): [0, 1, 67, 3, 4, 5, 6, 7, 8, 9],
 (6, 8): [0, 1, 68, 3, 4, 5, 6, 7, 8, 9],
 (6, 9): [0, 1, 69, 3, 4, 5, 6, 7, 8, 9],
 (7, 0): [0, 1, 70, 3, 4, 5, 6, 7, 8, 9],
 (7, 1): [0, 1, 71, 3, 4, 5, 6, 7, 8, 9],
 (7, 2): [0, 1, 72, 3, 4, 5, 6, 7, 8, 9],
 (7, 3): [0, 1, 73, 3, 4, 5, 6, 7, 8, 9],
 (7, 4): [0, 1, 74, 3, 4, 5, 6, 7, 8, 9],
 (7, 5): [0, 1, 75, 3, 4, 5, 6, 7, 8, 9],
 (7, 6): [0, 1, 76, 3, 4, 5, 6, 7, 8, 9],
 (7, 7): [0, 1, 77, 3, 4, 5, 6, 7, 8, 9],
 (7, 8): [0, 1, 78, 3, 4, 5, 6, 7, 8, 9],
 (7, 9): [0, 1, 79, 3, 4, 5, 6, 7, 8, 9],
 (8, 0): [0, 1, 80, 3, 4, 5, 6, 7, 8, 9],
 (8, 1): [0, 1, 81, 3, 4, 5, 6, 7, 8, 9],
 (8, 2): [0, 1, 82, 3, 4, 5, 6, 7, 8, 9],
 (8, 3): [0, 1, 83, 3, 4, 5, 6, 7, 8, 9],
 (8, 4): [0, 1, 84, 3, 4, 5, 6, 7, 8, 9],
 (8, 5): [0, 1, 85, 3, 4, 5, 6, 7, 8, 9],
 (8, 6): [0, 1, 86, 3, 4, 5, 6, 7, 8, 9],
 (8, 7): [0, 1, 87, 3, 4, 5, 6, 7, 8, 9],
 (8, 8): [0, 1, 88, 3, 4, 5, 6, 7, 8, 9],
 (8, 9): [0, 1, 89, 3, 4, 5, 6, 7, 8, 9],
 (9, 0): [0, 1, 90, 3, 4, 5, 6, 7, 8, 9],
 (9, 1): [0, 1, 91, 3, 4, 5, 6, 7, 8, 9],
 (9, 2): [0, 1, 92, 3, 4, 5, 6, 7, 8, 9],
 (9, 3): [0, 1, 93, 3, 4, 5, 6, 7, 8, 9],
 (9, 4): [0, 1, 94, 3, 4, 5, 6, 7, 8, 9],
 (9, 5): [0, 1, 95, 3, 4, 5, 6, 7, 8, 9],
 (9, 6): [0, 1, 96, 3, 4, 5, 6, 7, 8, 9],
 (9, 7): [0, 1, 97, 3, 4, 5, 6, 7, 8, 9],
 (9, 8): [0, 1, 98, 3, 4, 5, 6, 7, 8, 9],
 (9, 9): [0, 1, 99, 3, 4, 5, 6, 7, 8, 9]}

你可以在这里使用 numpy，快速索引（更快的是 cython memoryview 所以也看看它）：

matrix=np.zeros((100,10),dtype=int)
list=[0,1,2,3,4,5,6,7,8,9]
def board(matrix):
    for x in range(10):
        for y in range(10):
            matrix[x*10+y]=1 #but here You populate whole sub-array of shape (10) with 1, so it will be: [1,1,1,1...,1] 
    print matrix
    for k in range(matrix.shape[0]):
        matrix[k]=list

board(matrix)
ppr(matrix)

for k in range(matrix.shape[0]):
    matrix[k,2]=k
ppr(matrix)

python: FOR 循环，迭代赋值未分配正确的值

python: FOR loop, Iterating assignment not assigning correct value

python

iteration

nested

list

assign