Python从门到精通(九):numpy科学计算库

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Numpy

这是一个三方的库，是很多科学与工程库的基础。在机器学习中应用广泛。

import numpy as np。

数组运算

import numpy as np

ax = np.array([1, 2, 3, 4])
ay = np.array([5, 6, 7, 8])

type(ax)
print(f'{ax} * 2 = {ax * 2}') #[2 4 6 8]
print(f'{ax} + 10 = {ax + 10}') #[11 12 13 14]

矩阵运算

import numpy as np
"""
[[ 1 -2  3]
 [ 0  4  5]
 [ 7  8 -9]]
"""
m = np.matrix([[1,-2,3],[0,4,5],[7,8,-9]])
print(f'm is:\n{m}')

"""
[[ 1  0  7]
 [-2  4  8]
 [ 3  5 -9]]
"""
print(f'm.T is:\n{m.T}')
"""
[[ 0.33043478 -0.02608696  0.09565217]
 [-0.15217391  0.13043478  0.02173913]
 [ 0.12173913  0.09565217 -0.0173913 ]]
"""
print(f'm.I is:\n{m.I}')

v = np.matrix([[2],[3],[4]])
print(f'v is:\n{v}')
"""
[[ 8]
 [32]
 [ 2]]
"""
print(f'm * v is:\n{m * v}')

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