python print redirection: stdin, stdout, stderr

redirect read 
import sys

name=input('please enter your name：')
print(name)

print('please enter your name：')
name=sys.stdin.readline() #redirect   read
 print (name)

f=open('e:/kangyujiao/test.txt','r')
sys.stdin=f
name=sys.stdin.readline() #redirect   read
 print (name)

class A:
    def read(self):
        return 'aaaaaaa'

sys.stdin=A()
name=sys.stdin.read() #redirect    read
 print (name)

redirect output

import sys

print('aaaaaaa')

old=sys.stdout
sys.stdout= open ( 'e:/kangyujiao/test.txt' , 'w' )
 print ( 'bbbbbbbb' )   #Redirect the output to the specified file
 sys.stdout=old
 print ( 'ccccccc' )

f= open ( 'e:/kangyuujiao/test.txt' , 'a' )
 print ( 'ddddddd' , file =f)    #redirect to append to the specified file
 class A:
     def write( self ,s):
         print ( s)


f=A()
print ( 'eeeeeee' , file =f)    #Redirect output, as long as there is a write method

output exception

import sys
 print ( 'aaaaaa' , file =sys.stderr) #The    output is abnormal, the red text is displayed