python numpy 数组中元素大于等于0的元素 

 1 >>> import numpy as np
 2 >>> a = np.random.randint(-5, 5, (5, 5))
 3 >>> a
 4 array([[-4, -4, -5,  2,  1],
 5        [-1, -2, -1,  3,  3],
 6        [-1, -2,  3, -5,  3],
 7        [ 0, -3, -5,  1, -4],
 8        [ 0,  3,  1,  3, -4]])
 9 # 方式一
10 >>> np.maximum(a, 0)
11 array([[0, 0, 0, 2, 1],
12        [0, 0, 0, 3, 3],
13        [0, 0, 3, 0, 3],
14        [0, 0, 0, 1, 0],
15        [0, 3, 1, 3, 0]])
16 # 方式二
17 >>> (a + abs(a)) / 2
18 array([[0, 0, 0, 2, 1],
19        [0, 0, 0, 3, 3],
20        [0, 0, 3, 0, 3],
21        [0, 0, 0, 1, 0],
22        [0, 3, 1, 3, 0]])
23 # 方式三
24 >>> b = a.copy()
25 >>> b[b < 0] = 0
26 >>> b
27 array([[0, 0, 0, 2, 1],
28        [0, 0, 0, 3, 3],
29        [0, 0, 3, 0, 3],
30        [0, 0, 0, 1, 0],
31        [0, 3, 1, 3, 0]])
32 # 方式四
33 >>> np.where(a > 0, a, 0)
34 array([[0, 0, 0, 2, 1],
35        [0, 0, 0, 3, 3],
36        [0, 0, 3, 0, 3],
37        [0, 0, 0, 1, 0],
38        [0, 3, 1, 3, 0]])

 

posted @ 2019-02-01 14:01  salami_china  阅读(12040)  评论(0)    收藏  举报