python - 获取numpy数组中特定值的索引

Question

我知道了。 numpy 数组:

arr = [0,0,0,1,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,1]

这就是我如何获取数组中所有 0 的索引:

inds = []
for index,item in enumerate(arr):     
    if item == 0:
        inds.append(index)

是否有一个 numpy 函数可以做同样的事情？

Answer 1

你可以使用 numpy.argwhere正如@chappers 在评论中指出的那样:

arr = np.array([0,0,0,1,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,1])

In [34]: np.argwhere(arr == 0).flatten()
Out[34]:
array([ 0,  1,  2,  4,  5,  6,  7,  8,  9, 10, 12, 14, 16, 17, 18, 19, 20,
       21, 22, 23, 24, 25], dtype=int32)

或者使用 astype(bool) 的逆函数:

In [63]: (~arr.astype(bool)).nonzero()[0]
Out[63]:
array([ 0,  1,  2,  4,  5,  6,  7,  8,  9, 10, 12, 14, 16, 17, 18, 19, 20,
       21, 22, 23, 24, 25], dtype=int32)