1.numpy库导入
import numpy as np
这里的np是我们在使用库时起的别名。
2.numpy库中常用的内置函数
序号方法名说明1dot()点积运算(向量或矩阵乘法)2zreos(shape, dtype)shape:创建的新数组的形状(维度)dtype:创建新数组的数据类型。3sum()数组求和4max()、min()求最大最小值5abs()求绝对值6add([],x)数组中的数同时加x7log()对数函数8exp(x)返回e的x幂次方9random.randn(x)返回一个随机的x位向量
1. np.dot()
矩阵或向量乘法https://blog.csdn.net/meini32/article/details/126125740
2.np.zreos(shape, dtype)
import numpy as np
print(np.zeros([2,3],int))
3.np.sum()
import numpy as np
A = [1,2,3]
print(np.sum(A))
4.np.max()、min()
import numpy as np
A = [-1,2,-3]
print(np.max(A))
print(np.min(A))
5.np.abs()
import numpy as np
A = [-1,2,-3]
print(np.abs(A))
6.np.add
import numpy as np
A = [-1,2,-3]
print(np.add(A,3))
7.np.log()
import numpy as np
A = [10,2,3]
print(np.log2(4))
print(np.log(np.exp(1)))
print(np.log10(A))
8.np.exp()
import numpy as np
A = [1,2,3]
print(np.exp(1))
print(np.exp(A))
9.random.randn(x)
import numpy as np
print(np.random.randn(5))
3.案例
1.给出kal值,计算水果中的物质的卡路里占比
import numpy as np
fruit = np.array([[56.0,0.0,4.4,68.0],
[1.2,104.0,52.0,8.0],
[1.8,35.0,99.0,8.9]])
total_Kal = fruit.sum(0)
print(total_Kal)
KalPercent = (fruit/total_Kal)*100
print(KalPercent)
2.n维向量和n维向量的相乘 (数字/n*n矩阵)
import numpy as np
a=np.random.randn(3)*100
b=np.random.randn(3)*100
print(a)
print(b)
print(a*b)
print(np.dot(a,b))
a.shape = (3,1)
b.shape = (1,3)
print(np.dot(a,b))
//如果想要直接得到矩阵 可以直接在定义a、b时设置行或列
a=np.random.randn(3,1)*100
b=np.random.randn(1,3)*100
Original: https://blog.csdn.net/meini32/article/details/126129007
Author: 恶熊比比
Title: Python中的numpy库
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