Numpy入门练习

#numpy创建一维数组
import numpy as np
my_arry=np.array([1,2,3,4,5])
print (my_arry)
print(my_arry.shape)
my_new_arry=np.zeros((5))
print(my_new_arry)
my_new_arry1=np.ones((5))
print(my_new_arry1)
my_new_arry2=np.random.random((5))
print(my_new_arry2)


#numpy创建二维数组
import numpy as np

my_2d_arry=np.zeros((3,3))
print(my_2d_arry)
my_2d_arry1=np.ones((3,3))
print(my_2d_arry1)
my_arry1=np.array([[4,5],[5,6]])
print(my_arry1)
print(my_arry1[0][1])
my_array_column_2 = my_arry1[:, 1]
print (my_array_column_2)


#数组的加减乘除
import numpy as np
a = np.array([[1.0, 2.0], [3.0, 4.0]])
b = np.array([[5.0, 6.0], [7.0, 8.0]])
sum = a + b
difference = a - b
product = a * b
quotient = a / b
print ("Sum = ", sum )
print ("Difference = ", difference)
print ("Product = ", product )
print ("Quotient = ", quotient)

#numpy创建一维数组

F:anacondapython.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:anacondapython.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:anacondapython.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.]]