import numpy as np
print(np.arange(15))
a = np.arange(15).reshape(5,3) # 矩阵重组
print(a)
[ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14]
[[ 0 1 2]
[ 3 4 5]
[ 6 7 8]
[ 9 10 11]
[12 13 14]]
a.shape # 属性:矩阵的行列
(5, 3)
a.ndim # 矩阵纬度
2
a.dtype.name #矩阵类型
'int32'
a.size #矩阵元素数
15
b= np.zeros((2,4,5))
print(b)
b.ndim
[[[0. 0. 0. 0. 0.]
[0. 0. 0. 0. 0.]
[0. 0. 0. 0. 0.]
[0. 0. 0. 0. 0.]]
[[0. 0. 0. 0. 0.]
[0. 0. 0. 0. 0.]
[0. 0. 0. 0. 0.]
[0. 0. 0. 0. 0.]]]
3
np.zeros((3,4)) # 0矩阵
array([[0., 0., 0., 0.],
[0., 0., 0., 0.],
[0., 0., 0., 0.]])
np.ones((2,3,4),dtype=np.int32)
array([[[1, 1, 1, 1],
[1, 1, 1, 1],
[1, 1, 1, 1]],
[[1, 1, 1, 1],
[1, 1, 1, 1],
[1, 1, 1, 1]]])
np.arange(10,30,5) # 开始,结束,步长
array([10, 15, 20, 25])
np.arange(0,2,0.2)
array([0. , 0.2, 0.4, 0.6, 0.8, 1. , 1.2, 1.4, 1.6, 1.8])
np.arange(0,2,0.2).reshape(2,5)
array([[0. , 0.2, 0.4, 0.6, 0.8],
[1. , 1.2, 1.4, 1.6, 1.8]])
np.random.random((2,3)) # 随机生成
array([[0.82026386, 0.16358246, 0.24346123],
[0.67492434, 0.30967117, 0.20575276]])
from numpy import pi
np.linspace(0, 2*pi ,100) # 开始,结束,元素数。在区间内平均找到n个数
array([0. , 0.06346652, 0.12693304, 0.19039955, 0.25386607,
0.31733259, 0.38079911, 0.44426563, 0.50773215, 0.57119866,
0.63466518, 0.6981317 , 0.76159822, 0.82506474, 0.88853126,
0.95199777, 1.01546429, 1.07893081, 1.14239733, 1.20586385,
1.26933037, 1.33279688, 1.3962634 , 1.45972992, 1.52319644,
1.58666296, 1.65012947, 1.71359599, 1.77706251, 1.84052903,
1.90399555, 1.96746207, 2.03092858, 2.0943951 , 2.15786162,
2.22132814, 2.28479466, 2.34826118, 2.41172769, 2.47519421,
2.53866073, 2.60212725, 2.66559377, 2.72906028, 2.7925268 ,
2.85599332, 2.91945984, 2.98292636, 3.04639288, 3.10985939,
3.17332591, 3.23679243, 3.30025895, 3.36372547, 3.42719199,
3.4906585 , 3.55412502, 3.61759154, 3.68105806, 3.74452458,
3.8079911 , 3.87145761, 3.93492413, 3.99839065, 4.06185717,
4.12532369, 4.1887902 , 4.25225672, 4.31572324, 4.37918976,
4.44265628, 4.5061228 , 4.56958931, 4.63305583, 4.69652235,
4.75998887, 4.82345539, 4.88692191, 4.95038842, 5.01385494,
5.07732146, 5.14078798, 5.2042545 , 5.26772102, 5.33118753,
5.39465405, 5.45812057, 5.52158709, 5.58505361, 5.64852012,
5.71198664, 5.77545316, 5.83891968, 5.9023862 , 5.96585272,
6.02931923, 6.09278575, 6.15625227, 6.21971879, 6.28318531])
# numpy arrays加减乘除运算
a = np.array([20,30,40,50])
b = np.arange(4)
print(a)
print(b)
[20 30 40 50]
[0 1 2 3]
c=a-b
print(c)
[20 29 38 47]
c=c-1
print(c)
[19 28 37 46]
print(b**2)
[0 1 4 9]
print(a<35)
[ True True False False]
print(a*b) # 求内积
[ 0 30 80 150]
print(a)
print(b)
print(a.dot(b)) # 该函数的作用是获取两个元素a,b的乘积. 30+80+150=260
[20 30 40 50]
[0 1 2 3]
260
print(np.dot(a,b)) # 该函数的作用是获取两个元素a,b的乘积.
260