python numpy库

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记录几个numpy中经常用到的函数

创建数组

NumPy 的核心是数组（arrays）。具体来说是多维数组（ndarrays）

import numpy as npa = np.array((0, 1, 2, 3, 4))b = np.array([0, 1, 2, 3, 4])c = np.arange(5)d = np.linspace(0, 10, 5) #[  0.    2.5   5.    7.5  10. ]分成五份print aprint bprint cprint d

[0 1 2 3 4]
[0 1 2 3 4]
[0 1 2 3 4]
[ 0. 2.5 5. 7.5 10. ]

import numpy as npa = np.array([[11, 12, 13, 14, 15],              [16, 17, 18, 19, 20],              [21, 22, 23, 24, 25],              [26, 27, 28, 29, 30],              [31, 32, 33, 34, 35]])print a[2][2] # 23

import numpy as npa = np.array([[11, 12, 13, 14, 15],              [16, 17, 18, 19, 20],              [21, 22, 23, 24, 25],              [26, 27, 28, 29, 30],              [31, 32, 33, 34, 35]])print a[2][2]         #a[2,2]          23print a[0][1:4]       #a[0,1:4]          [12 13 14]print a[::2, ::2]     #[[11 13 15]                       # [21 23 25]                       # [31 33 35]]print a[:,1]          #[12 17 22 27 32]

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