PuLP：目標函數：連接多個lpSum

Question

我試圖將幾個lpSum表達式連接為一個長表達式，這將是我的目標函數。 但是，我嘗試以優雅的方式合並這些表達式會導致不良結果。

我想要這樣的東西：

a = pulp.lpSum(...)
b = pulp.lpSum(...)
c = pulp.lpSum(...)

prob += a + b - c

我的代碼更具體：

    alloc_prob = pulp.LpProblem("Supplier Allocation Problem", pulp.LpMinimize)

    TPC_func = pulp.lpSum(X[s][p]*procCosts[s][p] for s in supplier for p in 
    project), "Total Procurement Costs"
    TTC_func = pulp.lpSum(X[s][p]*transCosts[s][p] for s in supplier for p in 
    project), "Total Transportation Costs (incl. taxes/duties)"
    TD_func = pulp.lpSum(X_SEP[c][1]*discountFactor['Bonus / ton [€/t]'][c] for 
    c in company), "Total Discounts"`

    # Objective function: TPC + TTC - TD -> min
    alloc_prob += TPC_func  + TTC_func - TD_func

我已經嘗試了不同的嵌套方法，例如：

    prob += [pulp.lpSum(X[s][p]*procCosts[s][p] + X[s][p]*transCosts[s][p] for s 
    in supplier for p in project) - pulp.lpSum(X_SEP[c][1]*discountFactor['Bonus 
    / ton [€/t]'][c] for c in company)]

輸出會執行應有的操作。 但是，這既不是很好的代碼，也不能分配給目標函數。 有沒有明智的實施方式？

謝謝！

Answer 1

沒有看到錯誤，我可以百分百確定，但是我認為您在lpsum中包含的名稱引起了問題，請嘗試以下操作

alloc_prob = pulp.LpProblem("Supplier Allocation Problem", pulp.LpMinimize)

TPC_func = pulp.lpSum(X[s][p]*procCosts[s][p] for s in supplier for p in 
project)
TTC_func = pulp.lpSum(X[s][p]*transCosts[s][p] for s in supplier for p in 
project)
TD_func = pulp.lpSum(X_SEP[c][1]*discountFactor['Bonus / ton [€/t]'][c] for 
c in company)

# Objective function: TPC + TTC - TD -> min
alloc_prob += TPC_func  + TTC_func - TD_func