NameError at / free variable 'y' 在封闭范围内赋值前被引用

Question

我需要为我的大学做一个小项目 - 创建 webapp 来解决交通问题，我正在制作 MVP 版本。我将 Django 用于 webapp，将 PuLP 用于传输问题部分。

启动我的问题解决逻辑时收到错误消息：

NameError at / free variable 'y' referenced before assignment in enclosing scope

行：

prob += lpSum([route_vars[x][y] for x in Distributors]) <= supply[x], "Sum of Products out of Warehouse %s"%x

我正在使用他们 GitHub here

中的 PuLP 示例

我这部分的代码如下：

    Warehouses = [0,1,2]
    supply = { 0: deliver1,
              1: deliver2,
              2: deliver3
              }
    Distributors = [0, 1, 2]
    demand = { 0: receiver1,
               1: receiver2,
               2: receiver3
              }

    costs = [   #dsitributors -static variables for debugging will change that later on
        #D  E  F
        [3, 5, 7],#A  Warehouse
        [12, 10, 9],#B  Warehouse
        [13, 3, 9],#C  Warehouse

    ]

    prob = LpProblem("Transportation Problem",LpMinimize)



    Routes = [(x,y) for x in Warehouses for y in Distributors]
    route_vars = LpVariable.dicts("Route",(Warehouses,Distributors),0,None,LpInteger)

    prob += lpSum([route_vars[x][y]*costs[x][y] for (x,y) in Routes]), "Sum of Transporting Costs"
    for x in Warehouses:
        prob += lpSum([route_vars[x][y] for x in Distributors]) <= supply[x], "Sum of Products out of Warehouse %s"%x

    for y in Distributors:
        prob += lpSum([route_vars[x][y] for y in Warehouses]) >= demand[y], "Sum of Products into Distributors %s"%y    


    prob.writeLP("TransportationProblem.lp")
    prob.solve()
    print("Status:", LpStatus[prob.status])
    for v in prob.variables():
        print(v.name, "=", v.varValue)
    print("Total Cost of transportation = ", value(prob.objective))

我想那只是我犯的一些愚蠢的错误，但无法真正找到它...另外，我通过数字而不是名称来命名仓库和分销商是我接收

的解决方法

TypeError: list indices must be integers or slices, not str

同一行。

Answer 1

在供应约束中，将Distributors赋值给y（目前y未定义），像这样：

for x in Warehouses:
    prob += lpSum([route_vars[x][y] for y in Distributors]) <= supply[x], "Sum of Products out of Warehouse %s"%x

同样的错误适用于需求约束，其中 Warehouses 应分配给 x。

对于部署 Apache，mod_wsgi 是一种选择。 https://docs.djangoproject.com/en/3.0/howto/deployment/wsgi/modwsgi/

NameError at / free variable 'y' 在封闭范围内赋值前被引用

NameError at / free variable 'y' referenced before assignment in enclosing scope

python

django

mathematical-optimization

pulp