Python 在元组列表中找到最接近的浮点值

Question

我有一个值 total_weight = 212.0，我的程序中有一部分试图找到准确的值，但我的列表中没有准确的权重。

所以我想得到最接近的值。在此示例中，它将是 [(200.0, (2.5, 5.0, 10.0, 15.0, 45.0)), (200.0, (2.5, 5.0, 10.0, 25.0, 35.0)), (220.0, (2.5, 5.0, 10.0, 25.0, 45.0))]

List = [ (180.0, (2.5, 5.0, 10.0, 15.0, 35.0)), (200.0, (2.5, 5.0, 10.0, 15.0, 45.0)), (200.0, (2.5, 5.0, 10.0, 25.0, 35.0)), (220.0, (2.5, 5.0, 10.0, 25.0, 45.0)), (240.0, (2.5, 5.0, 10.0, 35.0, 45.0)), (210.0, (2.5, 5.0, 15.0, 25.0, 35.0)), (230.0, (2.5, 5.0, 15.0, 25.0, 45.0)), (250.0, (2.5, 5.0, 15.0, 35.0, 45.0)), (270.0, (2.5, 5.0, 25.0, 35.0, 45.0)), (220.0, (2.5, 10.0, 15.0, 25.0, 35.0)), (240.0, (2.5, 10.0, 15.0, 25.0, 45.0)), (260.0, (2.5, 10.0, 15.0, 35.0, 45.0)), (280.0, (2.5, 10.0, 25.0, 35.0, 45.0)), (290.0, (2.5, 15.0, 25.0, 35.0, 45.0)), (225.0, (5.0, 10.0, 15.0, 25.0, 35.0)), (245.0, (5.0, 10.0, 15.0, 25.0, 45.0)), (265.0, (5.0, 10.0, 15.0, 35.0, 45.0)))]

我试过使用 min() 但我没能成功。

Answer 1

要找到最近的值，请将 min 与 key 函数一起使用，该函数给出与目标的距离：

>>> weights = [
    (180.0, (2.5, 5.0, 10.0, 15.0, 35.0)), 
    (200.0, (2.5, 5.0, 10.0, 15.0, 45.0)), 
    (200.0, (2.5, 5.0, 10.0, 25.0, 35.0)), 
    (220.0, (2.5, 5.0, 10.0, 25.0, 45.0)), 
    (240.0, (2.5, 5.0, 10.0, 35.0, 45.0)), 
    (210.0, (2.5, 5.0, 15.0, 25.0, 35.0)), 
    (230.0, (2.5, 5.0, 15.0, 25.0, 45.0)), 
    (250.0, (2.5, 5.0, 15.0, 35.0, 45.0)), 
    (270.0, (2.5, 5.0, 25.0, 35.0, 45.0)), 
    (220.0, (2.5, 10.0, 15.0, 25.0, 35.0)), 
    (240.0, (2.5, 10.0, 15.0, 25.0, 45.0)), 
    (260.0, (2.5, 10.0, 15.0, 35.0, 45.0)), 
    (280.0, (2.5, 10.0, 25.0, 35.0, 45.0)), 
    (290.0, (2.5, 15.0, 25.0, 35.0, 45.0)), 
    (225.0, (5.0, 10.0, 15.0, 25.0, 35.0)), 
    (245.0, (5.0, 10.0, 15.0, 25.0, 45.0)), 
    (265.0, (5.0, 10.0, 15.0, 35.0, 45.0)),
]
>>> total_weight = 212.0
>>> min(weights, key=lambda w: abs(w[0] - total_weight))
(210.0, (2.5, 5.0, 15.0, 25.0, 35.0))

要找到较高值和较低值，排序并找到第一个较高值的索引，然后取它和前一个：

>>> weights.sort()
>>> higher = next(i for i in range(len(weights)) if weights[i][0] > total_weight)
>>> weights[higher-1:higher+1]
[(210.0, (2.5, 5.0, 15.0, 25.0, 35.0)), (220.0, (2.5, 5.0, 10.0, 25.0, 45.0))]

（处理边缘情况会增加更多的复杂性——如果是完全匹配怎么办？如果目标高于或低于所有值怎么办？等等）

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