Python：根据列表中的索引循环遍历二维列表

Question

我有这个清单：

ls = [[0, [1, 5], [], 'A'],
      [1, [0, 2, 4], [], 'B'],
      [2, [3, 1], [], 'X'],
      [3, [2], [], 'C'],
      [4, [1], [], 'D'],
      [5, [0], [], 'E']]

我想遍历这个列表，从最后一项为“X”的行开始。在该行中，倒数第二项应为 0。之后，我想遍历同一行（第 3 行和第 1 行）第二列中显示的行，在这些行中，倒数第二项应为 1。然后我遍历第 0 行和第 4 行，倒数第二个项目应该是 2（此时无需遍历第 2 行，因为它已经被遍历了）。该迭代一直持续到整个倒数第二列被填满。所以输出应该是：

[[0, [1, 5], 2, 'A'],
 [1, [0, 2, 4], 1, 'B'],
 [2, [3, 1], 0, 'X'],
 [3, [2], 1, 'C'],
 [4, [1], 2, 'D'],
 [5, [0], 3, 'E']]

我尝试过这样做：

def foo(data):
    new_data = data
    for subls in new_data:
        if subls[3] == "X":
            start = subls[1]
            subls[2] = 0
    num = 1
    for num, item in enumerate(start):
        new_data[item][2] = num
        new_start = list(new_data[n][1] for n, i in enumerate(new_data))
        start = new_start
    num += 1
    return new_data

f = foo(ls)
for a in f:
    print(a)

但我只得到：

[0, [1, 5], [], 'A']
[1, [0, 2, 4], 1, 'B']
[2, [3, 1], 0, 'X']
[3, [2], 0, 'C']
[4, [1], [], 'D']
[5, [0], [], 'E']

我怎样才能做到这一点？

编辑@SaltySoda

起初这似乎可行，但当我尝试此列表时：

ls = [[0, [1, 7, 8, 9], [], 'E'],
        [1, [0, 2, 10, 11], [], 'C'],
        [2, [1, 3, 12, 13], [], 'C'],
        [3, [2, 4, 14, 15], [], 'C'],
        [4, [3, 5, 16, 17], [], 'C'],
        [5, [4, 6, 18, 19], [], 'C'],
        [6, [5, 20, 21, 22], [], 'E'],
        [7, [0], [], '-'],
        [8, [0], [], '-'],
        [9, [0], [], '-'],
        [10, [1], [], '-'],
        [11, [1], [], '-'],
        [12, [2], [], '-'],
        [13, [2], [], '-'],
        [14, [3], [], '-'],
        [15, [3], [], '-'],
        [16, [4], [], '-'],
        [17, [4], [], '-'],
        [18, [5], [], 'X'],
        [19, [5], [], '-'],
        [20, [6], [], '-'],
        [21, [6], [], '-'],
        [22, [6], [], '-']]

上面写着：

a[2] = a[2] - 1
TypeError: unsupported operand type(s) for -: 'list' and 'int'

您能否解释一下为什么会发生这种情况以及如何修复此错误？

Answer 1

试试这个：

def foo(data):
    num=2
    new_data = data
    for lists in new_data:
        if lists[3]=="X":
            break
        else:
            lists[2]=num
            num-=1
            ls2.append(lists)
            #ls.remove(lists)
    for times in ls2:
        ls.remove(times)
    
    
    
    x=0
    for lss in new_data:
        lss[2]=x
        x+=1
        ls2.append(lss)
    return ls
    
ls = [[0, [1, 5], [], 'A'],
      [1, [0, 2, 4], [], 'B'],
      [2, [3, 1], [], 'X'],
      [3, [2], [], 'C'],
      [4, [1], [], 'D'],
      [5, [0], [], 'E']]
ls2 = [] #== list where the elements are added
f = foo(ls)
for new_datas in ls2:
    print(new_datas)
    

Answer 2

我会做这样的事情。首先通过这个函数获取以'X'结尾的行。

def get_row_X_index(lst):
    for i in range(len(lst)):
        if lst[i][-1] == 'X':
            return i

然后遍历整个列表，并通过测量与末尾包含'X' 的行的距离来填充每行的倒数第二个值。

for i in range(len(ls)):
    ls[i][-2] = abs(X_row_index-i)

完整代码：

ls = [[0, [1, 5], [], 'A'],
      [1, [0, 2, 4], [], 'B'],
      [2, [3, 1], [], 'X'],
      [3, [2], [], 'C'],
      [4, [1], [], 'D'],
      [5, [0], [], 'E']]


def get_row_X_index(lst):
    for i in range(len(lst)):
        if lst[i][-1] == 'X':
            return i

X_row_index = get_row_X_index(ls)
print(X_row_index)

for i in range(len(ls)):
    ls[i][-2] = abs(X_row_index-i)

print(ls)

打印出来：

[[0, [1, 5], 2, 'A'], 
[1, [0, 2, 4], 1, 'B'], 
[2, [3, 1], 0, 'X'], 
[3, [2], 1, 'C'], 
[4, [1], 2, 'D'], 
[5, [0], 3, 'E']]

Answer 3

def foo(data, rows, num):
    next_rows = []
    next_num = num + 1
    for row in rows:
        if data[row][2]:
            continue
        else:
            next_rows.extend(data[row][1])
            data[row][2] = num
    return data, next_rows, next_num


def foo_whole(data):
    rows = []
    num = 1
    for subls in data:
        if subls[3] == "X":
            rows = [subls[0]]
    for subls in data:
        if not subls[2]:
            data, rows, num = foo(data, rows, num)
    for a in data:
        a[2] = a[2] - 1
    return data


if __name__ == '__main__':
    old_data = [[0, [1, 5], [], 'A'],
                [1, [0, 2, 4], [], 'B'],
                [2, [3, 1], [], 'X'],
                [3, [2], [], 'C'],
                [4, [1], [], 'D'],
                [5, [0], [], 'E']]
    new_data = foo_whole(old_data)
    for a in new_data:
        print(a)