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]])
