Python KeyError:0疑难解答

Question

一般来说，我不熟悉Gurobi和Python，每当我运行代码（这显然不完整，但我的教授鼓励我们在编写代码时运行代码，因为这样更容易排除故障），我就会在第27行（这是最后一行）上不断得到错误代码“KeyError:0”

我在多个论坛上读过这意味着什么（它试图从字典中访问键“0”的值，而该键在该字典中不存在（或未初始化），但仍然没有真正理解它

from gurobipy import *

# Sets
SetA = ["a", "b", "c", "d", "e"]
SetB = ["f", "g", "h", "i", "j",
   "k", "l", "m", "n", "o"]

A = range(len(SetA))
B = range(len(SetB))

# Data
PC = 100
X = [1, 2, 3, 4, 5]
D = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Y = [
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
[11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
[21, 22, 23, 24, 25, 26, 27, 28, 29, 30],
[31, 32, 33, 34, 35, 36, 37, 38, 39, 40],
[41, 42, 43, 44, 45, 46, 47, 48, 49, 50]
]

m = Model("Problem 2")

# Variables
Z = {(a,b): m.addVar() for a in A for b in B}

# Objective
m.setObjective(quicksum((PC+X[a]+Y[a][b])*Z[a][b] for a in A for b in B), GRB.MINIMIZE)

Answer 1

解决方案：

将最后一行更改为：

 m.setObjective(quicksum((PC+X[a]+Y[a][b])*Z[a,b] for a in A for b in B), GRB.MINIMIZE)