如何在元组列表中找到第一次的最大绝对索引？

Question

给定一个元组列表：

[(-8.33958, -84.01769099999999), (-7.96129, -84.37399199999999), (-8.33958, -83.84126699999999), (-7.96129, -84.19756499999998), (-7.24097, -85.581651), (-6.86267, -85.937952), (-7.24097, -85.405227), (-6.86267, -85.76152499999999), (-9.4382, -83.473767), (-9.4382, -83.473767), (-8.35625, -85.11197399999999), (-9.0599, -83.83006499999999), (-9.0599, -83.83006499999999), (-7.97795, -85.46824499999998), (-8.35625, -84.93524699999999), (-7.97795, -85.29151799999998), (-8.33958, -85.03772699999999), (-8.00311, -88.17046199999997), (-5.88285, -86.59070369999999), (-6.86267, -88.655385), (-9.37174, -86.88101999999999), (-7.34506, -88.24291199999999), (-8.22317, -87.13259099999999), (-7.72054, -86.124309), (-8.35625, -86.131707), (-8.35625, -86.131707), (-7.03703, -88.90182), (-8.51394, -86.422992), (-8.51394, -85.83968999999999), (-9.61255, -85.510092), (-9.89311, -84.10327799999999), (-7.96129, -87.540312), (-9.13791, -86.022645)]

目的是找到元组中第一项的最大值的索引。使用上面的示例输入输出元组的索引 (-9.89311, -84.10327799999999)

我一直这样做（但它没有 return 正确的输出）：

x = [(-8.33958, -84.01769099999999), (-7.96129, -84.37399199999999), (-8.33958, -83.84126699999999), (-7.96129, -84.19756499999998), (-7.24097, -85.581651), (-6.86267, -85.937952), (-7.24097, -85.405227), (-6.86267, -85.76152499999999), (-9.4382, -83.473767), (-9.4382, -83.473767), (-8.35625, -85.11197399999999), (-9.0599, -83.83006499999999), (-9.0599, -83.83006499999999), (-7.97795, -85.46824499999998), (-8.35625, -84.93524699999999), (-7.97795, -85.29151799999998), (-8.33958, -85.03772699999999), (-8.00311, -88.17046199999997), (-5.88285, -86.59070369999999), (-6.86267, -88.655385), (-9.37174, -86.88101999999999), (-7.34506, -88.24291199999999), (-8.22317, -87.13259099999999), (-7.72054, -86.124309), (-8.35625, -86.131707), (-8.35625, -86.131707), (-7.03703, -88.90182), (-8.51394, -86.422992), (-8.51394, -85.83968999999999), (-9.61255, -85.510092), (-9.89311, -84.10327799999999), (-7.96129, -87.540312), (-9.13791, -86.022645)]


index_of_max_abs_j = -1
for i, (j,k) in enumerate(x):
    if j*j > index_of_max_abs_j:
        index_of_max_abs_j = i
print index_of_max_abs_j

代码 return 是 max(j*j) 的索引，但对吗？它与尝试查找 max(|j|) 不同吗？

但是还有另一种方法可以实现相同的输出吗？ 也许 sorted 和 reverse 以及 key 和一些 math.abs？ sorted、reverse and/or key 的替代方案是否更有效？

如果元组列表中有任何项具有相同的值，return 最大绝对值的第一个实例的第一个索引。

Answer 1

我不确定您为什么要将元组第一个元素的值与索引进行比较，但这会为您提供第一个元素绝对值最高的元组索引。

max_index = -1
max_value = 0
for i, z in enumerate(x):
    value = abs(z[0])
    if value > max_value:
        max_index = i
        max_value = value

print(x[max_index])

或者作为一种可读性较差的单行，

print(x.index(max(x, key=lambda y:abs(y[0]))))

Answer 2

您可以分两步完成，根据第 1 步中的第一个键获取最大值，然后使用元素获取索引

>>> max_value = sorted(x, key=lambda y: y[0])[0]

>>> x.index(max_value)

30

Answer 3

这是一个替代方案，提供时没有对效率发表评论：

y = [abs(item[0]) for item in x]
m = max(y)
print(y.index(m))

Answer 4

print(max((abs(value[0]),index) for (index,value) in enumerate(values))[1]

将在一次传递中给出具有最大元素的最后一个元素的索引具有本机功能，所以应该是最快的方法

如果你真的想拥有最大元素中的第一个，你可以这样做

print(-max((abs(value[0]),-index) for (index,value) in enumerate(values))[1])

如何在元组列表中找到第一次的最大绝对索引？

How to find the index of the maximum absolute of the first time in a list of tuples?

python

sorting

tuples

max

absolute