如何獲取numpy array前N個最大值

numpy.argsort(a, axis=-1, kind='quicksort', order=None)
'''
Returns the indices that would sort an array.
Perform an indirect sort along the given axis using the algorithm specified by the kind keyword. It returns an array of indices of the same shape as a that index data along the given axis in sorted order.
'''
Parameters: 
a : array_like
Array to sort.
 
axis : int or None, optional
Axis along which to sort. The default is -1 (the last axis). If None, the flattened array is used.
 
kind : {‘quicksort', ‘mergesort', ‘heapsort', ‘stable'}, optional
Sorting algorithm.
 
order : str or list of str, optional
When a is an array with fields defined, this argument specifies which fields to compare first, second, etc. A single field can be specified as a string, and not all fields need be specified, but unspecified fields will still be used, in the order in which they come up in the dtype, to break ties.
 
Returns: 
index_array : ndarray, int
Array of indices that sort a along the specified axis. If a is one-dimensional, a[index_array] yields a sorted a. More generally, np.take_along_axis(a, index_array, axis=a) always yields the sorted a, irrespective of dimensionality.
 

import numpy as np
top_k=3
arr = np.array([1, 3, 2, 4, 5])
top_k_idx=arr.argsort()[::-1][0:top_k]
print(top_k_idx)
#[4 3 1]

import numpy as np
a = np.array([1,4,3,5,2])
b = np.argsort(a)
print(b)

import heapq
 
a=[43,5,65,4,5,8,87]
re1 = heapq.nlargest(3, a) #求最大的三個元素，並排序
re2 = map(a.index, heapq.nlargest(3, a)) #求最大的三個索引    nsmallest與nlargest相反，求最小
print(re1)
print(list(re2)) #因為re2由map()生成的不是list，直接print不出來，添加list()就行瞭