numpy.nonzero(a)

Return the indices of the elements that are non-zero.

Returns a tuple of arrays, one for each dimension of a, containing the indices of the non-zero elements in that dimension. The values in aare always tested and returned in row-major, C-style order. The corresponding non-zero  values can be obtained with:

 

 

import numpy as npa = np.eye(3);print np.nonzero(a)#(array([0, 1, 2]), array([0, 1, 2]))

　　

print np.transpose(np.nonzero(a))#[[0 0]# [1 1]# [2 2]]