a = np.array([[1,2,3,4],[5,6,7,8],[9,10,11,12]]) >>> a array([[ 1, 2, 3, 4], [ 5, 6, 7, 8], [ 9, 10, 11, 12]])
>>> a[a[:,0] > 3] # select rows where first column is greater than 3
array([[ 5, 6, 7, 8],
[ 9, 10, 11, 12]])
>>> a[a[:,0] > 3][:,np.array([True, True, False, True])] # select columns
array([[ 5, 6, 8],
[ 9, 10, 12]])
# fancier equivalent of the prevIoUs
>>> a[np.ix_(a[:,0] > 3, np.array([True, True, False, True]))]
array([[ 5, 6, 8],
[ 9, 10, 12]])
最后，我们可以通过给出列号列表而不是乏味的布尔型掩码来简化操作：
>>> a[np.ix_(a[:,0] > 3, (0,1,3))]
array([[ 5, 6, 8],
[ 9, 10, 12]])
602392714
清零编程群