字典中的 PuLP 变量定义

Question

我想用 PuLP 声明一组变量，其中包含以下列表的所有可能组合：

month = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
manufacturer = ['China', 'Mexico', 'Taiwan']
demand = ['London', 'Paris', 'Milan']

然后，我将有一个字典（例如）如下： '1.China.London'、'1.China.Paris'、...

我尝试了以下代码，但我不知道如何存储所有组合。

vlbs = {}
for key in month:
    for kay in manufacturer:
        for eyk in demand:
            vlbs = (str(key)+'.'+str(kay)+'.'+str(eyk))

首先，我没有正确地理解字典 vlbs。之后：

variables = {var: pl.LpVariable(var, lowBound = 0) for var in vlbs}

如何正确解决？

Answer 1

您可以使用元组作为字典键。我认为这使得 filtering/searching 比做一堆字符串连接和拆分更容易。

months = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
manufacturers = ['China', 'Mexico', 'Taiwan']
demands = ['London', 'Paris', 'Milan']

var_dict = {}

for month in months:
    for manufacturer in manufacturers:
        for demand in demands:
            combo = (month, manufacturer, demand)
            var_name = '.'.join([str(c) for c in combo])
            var_dict[combo] = LpVariable(var_name, lowBound=0) 

# add constraint for month 1
model += lpSum([k for k in var_dict if k[0] == 1]) <= 50

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