from unittest import result
import numpy as np
print(np.__version__)  #输出版本号

data1 = [6, 8.5, 9, 0]
arr1 = np.array(data1)
print(arr1)

print(arr1.dtype)  #默认保存为双精度（64 bit)浮点数

arr1 = arr1.astype(np.int32)  #转换为32位整数
print(arr1)

data2 = [[1, 2, 3, 4], [5, 6, 7, 8]] #这是一个两层嵌套列表
arr2 = np.array(data2)   #转换为一个二维数组
print(arr2)

#arange(start, stop, step, dtype)
arr3 = np.arange(10)  #生成0-9的ndarry数组
print(arr3)

arr4 = range(10)
print(arr4)

arr3 = arr3 + 1 
print(arr3)

print(type(arr3))
print(type(arr4))

np.arange(0, 10, .5)

A = np.array([[1, 1, 1],
            [2, 2, 2],
            [5, 5, 5]])
B = np.array([[0, 1, 0],
            [1, 1, 0],
            [1, 1, 1]])
result = A @ B  #等价于result = np.dot(A, B)
print(result)

result2 = np.einsum('ij,jk ->', A,B)
print(result2)