Numpy：判别运算取值

import numpy
print("-------------一维数组运算取值------------------")
vector = numpy.array([5, 10, 15, 20])
# vector == 10
equal_to_ten = (vector == 10)   
print (equal_to_ten)          # 返回：[False  True False False]
print(vector[equal_to_ten])   # 返回：[10]


print("---------------二维数组运算取值----------------------")
matrix = numpy.array([
                    [5, 10, 15], 
                    [20, 25, 30],
                    [35, 40, 45]
                 ])
print(matrix == 25)
print("------------")
second_column_25 = (matrix[:,1] == 25)
print (second_column_25)             # 返回：[False  True False]，第1个是真，可用来取值
print(matrix[second_column_25, :])  # 提取第1行所有列，返回：[[20 25 30]]