我有一个清单:
a = [32, 37, 28, 30, 37, 25, 27, 24, 35, 55, 23, 31, 55, 21, 40, 18, 50,
35, 41, 49, 37, 19, 40, 41, 31]
最大元素是55(两个元素在位置9和12)
我需要找到在哪个位置(s)的最大值是位于。请帮助。
我有一个清单:
a = [32, 37, 28, 30, 37, 25, 27, 24, 35, 55, 23, 31, 55, 21, 40, 18, 50,
35, 41, 49, 37, 19, 40, 41, 31]
最大元素是55(两个元素在位置9和12)
我需要找到在哪个位置(s)的最大值是位于。请帮助。
当前回答
>>> max(enumerate([1,2,3,32,1,5,7,9]),key=lambda x: x[1])
>>> (3, 32)
其他回答
a.index(max(a))
会告诉你列表a中值最大的元素的第一个实例的索引。
>>> m = max(a)
>>> [i for i, j in enumerate(a) if j == m]
[9, 12]
如果你想获取一个名为data的列表中最大n个数字的索引,你可以使用Pandas sort_values:
pd.Series(data).sort_values(ascending=False).index[0:n]
这里是最大值和它出现的索引:
>>> from collections import defaultdict
>>> d = defaultdict(list)
>>> a = [32, 37, 28, 30, 37, 25, 27, 24, 35, 55, 23, 31, 55, 21, 40, 18, 50, 35, 41, 49, 37, 19, 40, 41, 31]
>>> for i, x in enumerate(a):
... d[x].append(i)
...
>>> k = max(d.keys())
>>> print k, d[k]
55 [9, 12]
后来:为了满足@SilentGhost
>>> from itertools import takewhile
>>> import heapq
>>>
>>> def popper(heap):
... while heap:
... yield heapq.heappop(heap)
...
>>> a = [32, 37, 28, 30, 37, 25, 27, 24, 35, 55, 23, 31, 55, 21, 40, 18, 50, 35, 41, 49, 37, 19, 40, 41, 31]
>>> h = [(-x, i) for i, x in enumerate(a)]
>>> heapq.heapify(h)
>>>
>>> largest = heapq.heappop(h)
>>> indexes = [largest[1]] + [x[1] for x in takewhile(lambda large: large[0] == largest[0], popper(h))]
>>> print -largest[0], indexes
55 [9, 12]
你也可以使用numpy包:
import numpy as np
A = np.array(a)
maximum_indices = np.where(A==max(a))
这将返回包含max值的所有下标的numpy数组
如果你想把它变成一个列表:
maximum_indices_list = maximum_indices.tolist()