[英]KeyError: (1, 1) when trying to use python list comprehension and google- ortools
I used this example here if/else in a list comprehension for list comprehension with if-else to create a constraint for the sum .我在if/else 列表推导中使用了此示例,以使用 if-else 为列表推导创建 sum 约束。
This is the piece of code that triggers the error这是触发错误的一段代码
for j in range(1, m+1):
solver.Add(solver.Sum([0 if c[i][j]==0 else x[i, j] for i in range(1, n+1)]) <= 1)
x is a dict defined earlier and c[i][j] is a boolean that is 1 when (i,j) is in the permitted. x 是前面定义的字典,而 c[i][j] 是一个布尔值,当 (i,j) 在允许范围内时为 1。 But when (i,j) is in permitted x[i,j] holds a variable in ortools .
但是当 (i,j) 被允许时, x[i,j] 在 ortools 中保存一个变量。 So what I am saying is that I want for this particular j to sum x[i,j]'s , if x[i,j] exists then ok if it does not then just add 0 .
所以我要说的是,我希望这个特定的 j 对 x[i,j]'s 求和,如果 x[i,j] 存在,那么如果它不存在则可以,那么只需添加 0 。
c = [[0]*(m+1)]*(n+1)
for (i,j) in permitted:
c[i][j]=1
x = {}
for (i,j) in permittted:
x[i, j] = solver.IntVar(0, 1, '')
There is a problem with how your boolean list is defined.您的布尔列表的定义方式存在问题。 Consider this:
考虑一下:
In [1]: c = [[0] * 2] * 3
In [2]: c
Out[2]: [[0, 0], [0, 0], [0, 0]]
In [3]: c[1][1] = 1
In [4]: c
Out[4]: [[0, 1], [0, 1], [0, 1]]
In c
, you actually have the same inner list repeated, so assigning a single value is reflected in each copy.在
c
中,您实际上重复了相同的内部列表,因此分配单个值会反映在每个副本中。 Hence your checks for c[i][j] == 0
may not produce the results you expected.因此,您对
c[i][j] == 0
的检查可能不会产生您预期的结果。
Try changing the definition of c
to:尝试将
c
的定义更改为:
c = [[0] * (m + 1) for _ in range(n + 1)]
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