numpy矩阵操作

1. 构建对称矩阵

import numpy as np
import random

matrix = np.zeros((5, 5), dtype=int)
for i in range(5):
    for j in range(5):
        if j == i:
            matrix[i][j] = 1
        elif j > i:
            matrix[i][j] = random.randint(1, 10)
print(matrix)
# [[ 1  2  5  8  7]
#  [ 0  1  3 10  1]
#  [ 0  0  1 10  7]
#  [ 0  0  0  1  5]
#  [ 0  0  0  0  1]]
matrix += matrix.T - np.diag(matrix.diagonal())
print(matrix)
# [[ 1  2  5  8  7]
#  [ 2  1  3 10  1]
#  [ 5  3  1 10  7]
#  [ 8 10 10  1  5]
#  [ 7  1  7  5  1]]