数组：numpy.shape 与numpy.reshape函数

import numpy as np

a = np.array([1,2,3])
#a 
#array([1,2,3])

type(a)
#nympy.ndarray

a.shape
#(3,)   #一纬数据  看大小

a= a.reshape((1，-1) ) #明确行列，-1=3
a.shape
#(1,3)  #1行3列  

a = np.array([1,2,3,4,5,6])

a.shape

#(6,)

a= a.reshape((2,-1))
a.shape
#(2,3)  

a
#array（
    [[1,2,3],
    []4,5,6]
]
）

###
a= a.reshape((-1,2))
a
array([
    [1,2],
    [3,4],
    [5,6]
])

##取5
a[2,0]
## 将5换成55
a[2,0]= 55

a = zeros((3,3))

a

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

a = np.ones((2,3))

a

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

a = np.full((3,3),0)  #3行3列，所有数据都是0
a = np.full((2,3),1)  #2行3列，所有数据都是1

a = np.eye((3))  #左上右下为1，3行3列

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

a=np.random.random((3,4))  #3行4列，0-1之间数字组成的

array([[0.31970217, 0.52454361, 0.93528294, 0.59955502],
       [0.47355245, 0.7775892 , 0.8112688 , 0.58033926],
       [0.20438656, 0.37185309, 0.89225405, 0.61406772]])