Numpy入门练习
1 #numpy创建一维数组 2 import numpy as np 3 my_arry=np.array([1,2,3,4,5]) 4 print (my_arry) 5 print(my_arry.shape) 6 my_new_arry=np.zeros((5)) 7 print(my_new_arry) 8 my_new_arry1=np.ones((5)) 9 print(my_new_arry1) 10 my_new_arry2=np.random.random((5)) 11 print(my_new_arry2) 12 13 14 #numpy创建二维数组 15 import numpy as np 16 17 my_2d_arry=np.zeros((3,3)) 18 print(my_2d_arry) 19 my_2d_arry1=np.ones((3,3)) 20 print(my_2d_arry1) 21 my_arry1=np.array([[4,5],[5,6]]) 22 print(my_arry1) 23 print(my_arry1[0][1]) 24 my_array_column_2 = my_arry1[:, 1] 25 print (my_array_column_2) 26 27 28 #数组的加减乘除 29 import numpy as np 30 a = np.array([[1.0, 2.0], [3.0, 4.0]]) 31 b = np.array([[5.0, 6.0], [7.0, 8.0]]) 32 sum = a + b 33 difference = a - b 34 product = a * b 35 quotient = a / b 36 print ("Sum = ", sum ) 37 print ("Difference = ", difference) 38 print ("Product = ", product ) 39 print ("Quotient = ", quotient)
#numpy创建一维数组
F:\anaconda\python.exe F:/code/practice.py
[1 2 3 4 5]
(5,)
[0. 0. 0. 0. 0.]
[1. 1. 1. 1. 1.]
[0.43426558 0.12712648 0.26232948 0.98755646 0.65736363]
进程已结束,退出代码0
#numpy创建二维数组
F:\anaconda\python.exe F:/code/practice.py
[[0. 0. 0.]
[0. 0. 0.]
[0. 0. 0.]]
[[1. 1. 1.]
[1. 1. 1.]
[1. 1. 1.]]
[[4 5]
[5 6]]
5
[5 6]
进程已结束,退出代码0
#数组的加减乘除
F:\anaconda\python.exe F:/code/practice.py
Sum = [[ 6. 8.]
[10. 12.]]
Difference = [[-4. -4.]
[-4. -4.]]
Product = [[ 5. 12.]
[21. 32.]]
Quotient = [[0.2 0.33333333]
[0.42857143 0.5 ]]
进程已结束,退出代码0
如你所见，乘法运算符执行逐元素乘法而不是矩阵乘法。 要执行矩阵乘法，你可以执行以下操作：
matrix_product = a.dot(b)
print "Matrix Product = ", matrix_product输出将是：
[[19. 22.]
[43. 50.]]
