TypeError: 'int' object does not support item assignment

Answered

bo_o

December 17, 2023 14:50

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I try to get the solution
class Solution:
    ObjVal = 0
    X = [[[]]]
    Y = [[[[]]]]
    C = [[]]
    Ct = [[]]
    Vl = [[[]]]
    Vr = [[[]]]
    T = [[[]]]
    t = [[[[]]]]
    route_Truck = []
    route_UAV = []

    def getSolution(self, data, model):
        solution = Solution()
        solution.ObjVal = model.ObjVal
        # X_ijk
        solution.X = [[([0] * data.vehicleNum) for j in range(data.nodeNum)] for i in range(data.nodeNum)]
        # Y_ijkd
        solution.Y = [[([0] * data.nodeNum) for j in range(data.nodeNum)] for k in range(data.vehicleNum) for d in range(data.droneNum)]
        # C_ik, C_id
        solution.C = [([0] * data.vehicleNum) for i in range(data.nodeNum)]
        solution.Ct = [([0] * data.droneNum) for i in range(data.nodeNum)]
        # Vl, Vr
        solution.Vl = [[([0] * data.droneNum) for k in range(data.vehicleNum)] for i in range(data.nodeNum)]
        solution.Vr = [[([0] * data.droneNum) for k in range(data.vehicleNum)] for i in range(data.nodeNum)]
        # T_ijk, t_ijkd
        solution.T = [[([0] * data.vehicleNum) for j in range(data.nodeNum)] for i in range(data.nodeNum)]
        solution.t = [[([0] * data.droneNum) for k in range(data.vehicleNum)] for j in range(data.nodeNum) for i in range(data.nodeNum)]

        for m in model.getVars():
            str = re.split(r"_", m.VarName)
            if (str[0] == "X" and m.x == 1):
                solution.X[int(str[1])][int(str[2])][int(str[3])] = m.x
                print(str, end="")
                print(" = %d" % m.x)
            elif (str[0] == "Y" and m.x == 1):
                solution.Y[int(str[1])][int(str[2])][int(str[3])][int(str[4])] = m.x
            elif (str[0] == "C" and m.x == 1):
                solution.C[int(str[1])][int(str[2])] = m.x
            elif (str[0] == "Ct" and m.x == 1):
                solution.Ct[int(str[1])][int(str[2])] = m.x
            elif (str[0] == "Vl" and m.x == 1):
                solution.Vl[int(str[1])][int(str[2])][int(str[3])] = m.x
            elif (str[0] == "Vr" and m.x == 1):
                solution.Vr[int(str[1])][int(str[2])][int(str[3])] = m.x
            elif (str[0] == "T" and m.x > 0):
                solution.T[int(str[1])][int(str[2])][int(str[3])] = m.x
            elif (str[0] == "t" and m.x > 0):
                solution.t[int(str[1])][int(str[2])][int(str[3])][int(str[4])] = m.x
            elif (str[0] == "z" and m.x > 0):
                solution.z = m.x

solution.Y reports the error:
Traceback (most recent call last):
  File "E:/PycharmProjects/project/gurobi.py", line 560, in <module>
    solution = solution.getSolution(data, model)
  File "E:/PycharmProjects/project/gurobi.py", line 126, in getSolution
    solution.Y[int(str[1])][int(str[2])][int(str[3])][int(str[4])] = m.x
TypeError: 'int' object does not support item assignment

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 13, 2026 01:32

  This post is more than two years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
• 

  Maliheh Aramon

  • Gurobi Staff

  December 19, 2023 20:41

  This error is a Python error and is not related to Gurobi. 
  
  The error happens when an integer is made to act as a list. For example, the script below will generate the same error as you observed:

  A = [1, 2, 3]
  # A[2] is an integer and cannot be treated as a list
  A[2][0] = 4

  You might want to check the initialization of the \(\texttt{solution.Y}\) attribute in your code to ensure \(\texttt{solution.Y[i][j][k]}\) is a list and not an integer. 
  
  Best regards,
  Maliheh

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