numpy 返回函数的上三角矩阵

np.triu()

matrix2=np.triu(matrix1)

numpy.triu(m, k=0)[source]

Upper triangle of an array.

Return a copy of a matrix with the elements below the k-th diagonal zeroed.

np.triu([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1)
array([[ 1, 2, 3],
[ 4, 5, 6],
[ 0, 8, 9],
[ 0, 0, 12]])