numpy

import numpy as np

 

%通过链表创建数组
1 mylist = [1, 2, 3]
x = np.array(mylist)
x

array([1, 2, 3])

%直接创建数组
1 y = np.array([4, 5, 6])
y

array([4, 5, 6])

%创建多维数组
1 m = np.array([[7, 8, 9], [10, 11, 12]])
m

array([[ 7,  8,  9],
       [10, 11, 12]])

m.shape

(2, 3)

n = np.arange(0, 30, 2) # start at 0 count up by 2, stop before 30
n

array([ 0,  2,  4,  6,  8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28])

n = n.reshape(3, 5) # reshape array to be 3x5
n

array([[ 0,  2,  4,  6,  8],
       [10, 12, 14, 16, 18],
       [20, 22, 24, 26, 28]])

1 o = np.linspace(0, 4, 9) # return 9 evenly spaced values from 0 to 4
o

array([ 0. ,  0.5,  1. ,  1.5,  2. ,  2.5,  3. ,  3.5,  4. ])

o.resize(3, 3)
o

array([[ 0. ,  0.5,  1. ],
       [ 1.5,  2. ,  2.5],
       [ 3. ,  3.5,  4. ]])

np.ones((3, 2))

array([[ 1.,  1.],
       [ 1.,  1.],
       [ 1.,  1.]])

np.zeros((2, 3))

array([[ 0.,  0.,  0.],
       [ 0.,  0.,  0.]])

np.eye(3)

array([[ 1.,  0.,  0.],
       [ 0.,  1.,  0.],
       [ 0.,  0.,  1.]])

np.diag(y)

array([[4, 0, 0],
       [0, 5, 0],
       [0, 0, 6]])

np.array([1, 2, 3] * 3)

array([1, 2, 3, 1, 2, 3, 1, 2, 3])

np.repeat([1, 2, 3], 3)

array([1, 1, 1, 2, 2, 2, 3, 3, 3])

p = np.ones([2, 3], int)
p

array([[1, 1, 1],
       [1, 1, 1]])

np.vstack([p, 2*p])

array([[1, 1, 1],
       [1, 1, 1],
       [2, 2, 2],
       [2, 2, 2]])

np.hstack([p, 2*p])

array([[1, 1, 1, 2, 2, 2],
       [1, 1, 1, 2, 2, 2]])