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本文小编为大家详细介绍“如何获取numpy的array中前N个最大值”,内容详细,步骤清晰,细节处理妥当,希望这篇“如何获取numpy的array中前N个最大值”文章能帮助大家解决疑惑,下面跟着小编的思路慢慢深入,一起来学习新知识吧。
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]
补充:python topN / topK 取 最大的N个数 或 最小的N个数
import numpy as np a = np.array([1,4,3,5,2]) b = np.argsort(a) print(b)
print结果[0 4 2 1 3]
说明a[0]最小,a[3]最大
a[0]<a[4]<a[2]<a[1]<a[3]
补充:利用Python获取数组或列表中最大的N个数及其索引
import heapq a=[43,5,65,4,5,8,87] re1 = heapq.nlargest(3, a) #求最大的三个元素,并排序 re2 = map(a.index, heapq.nlargest(3, a)) #求最大的三个索引 nsmallest与nlargest相反,求最小 print(re1) print(list(re2)) #因为re2由map()生成的不是list,直接print不出来,添加list()就行了
结果:
re1:[87, 65, 43]
re2:[6, 2, 0]
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