python：ndarray基本操作2

import numpy as np
a=np.identity(4,dtype="int")
print(a)

arr=arr+1

import numpy as np
arr=np.array([1,0,0,0,
  2,1,0,0,
  3,0,1,0,
  4,0,0,1])
arr=arr.reshape(4,4)
arr[0]=arr[0]-arr[2]
arr=arr.reshape(1,16)
print(arr)

import numpy as np
arr=np.array(([-2,0,-1,0],
         [2,1,0,0],
         [3,0,1,0],
         [4,0,0,1]))
arr[0]=arr[0]+arr[2]
print(arr)

import numpy as np
arr=np.zeros((4,4),dtype="int")
arr[:,0]=1
print(arr)

import numpy as np
a=np.identity(4,dtype="int")
a[2]=a[2]+3   #第一种
print(a)
import numpy as np
#第二种
a[2][0]=3
a[2][1]=3
a[2][2]=4
a[2][3]=3

1.Bob ['Joe' 'Will' 'Bob'] ['Bob' 'Joe' 'Will' 'Bob' 'Will' 'Joe'
'Joe']
2.import numpy as np
  data=np.random.rand(4,7)
print(data)
3.这个需要自己写

import numpy as np
arr=np.array([1,0,0,0,
  2,1,0,0,
  3,0,1,0,
  4,0,0,1])
arr=arr.reshape(4,4)
i=1
while i<4:
    arr[i,0]=0
    i=i+1;
print(arr)

[[[ 2  3  4]
  [ 5  6  7]]
 [[ 7  8  9]
  [10 11 12]]]

[[42 42 42]
 [42 42 42]]

import numpy as np
arr=np.array([[0,1],[3,4]])
arr1=np.array([[0,1],[2,3]])
arr[0]=arr[0]+arr1[0]
arr[1]=arr[1]+arr1[1]
print(arr)

import numpy as np
arr = np.array([[0, 1, 2], [3, 4, 5]])
arr1 = np.array([[0, 1], [2, 3], [4, 5]])
print(arr)
print(arr1)
arr[0,0:2]=arr[0,0:2]+arr1[0]
arr[1,0:2]=arr[1,0:2]+arr1[1]
print(arr)