使用Python编辑文件中的单词

Question

I'm not getting the logic to edit a file in python which has following content:

session1: Part1
     host1:           #All the four host here should be user input 
     host2:
     host3:
     host4:
end

session2: Part2    #The UP,DOWN,LEFT,RIGHT values can be jumbled among sides                                            
 host1:
    up = host2  
 host2:
    down = host3
 host3:
    left = host4
 host4:
    right = host3

end

In first part of the file "session1" it should get either 2 or 3 or 4 inputs for host 1 to 4 as a string from user, and in second part of the file "session2" it has to update the same input accordingly in place of "host1 to 4:". But the sides (up,left,down,right) can be jumbled according to the user, means they can move the value of up to down or down to right or left but the "host1,2,3,4:" in "session2"should remains same. If it is not understandable, I can explain more, I have written this flaw code which is not writing back to the file, is there any way to do it better?

#!/usr/bin/python

File1 = open ("test","rw+")

Read1 = File1.read()

Spl = Read1.split()

Inp_Host = raw_input("Enter the host input:")

Side_screen = str(raw_input ("up, down, left, right, choose your way:"))

#if Inp_Host == Spl[2] or Spl [3] or Spl [4] or Spl [5]:
#   print "The host already exists"

#else:

if Side_screen == "up":
    Spl[2] = Spl[9] = Inp_Host
        Spl[12] = input ()

elif Side_screen == "down":
         Spl[3] = Spl[13] = Inp_Host
         Spl[16] = input ()

elif Side_screen == "left":
         Spl[4] = Spl[17] = Inp_Host
         Spl[20] = input ()

elif Side_screen == "right":
         Spl[5] = Spl[21] = Inp_Host
         Spl[24] = input ()

Spl.write()

print Spl.read()

And I'm not sure whether editing a file by splitting will put back the file in same indention or not.

Answer 1

There are a number of problems with your code. First of all, if you want to write to the file "test" in order to modify its contents, you will have to call file.write() , not Spl.write() . Also, I believe the file mode "rw+" is invalid; to open a file for both reading and writing, you would want just "r+" ; please see here for details. Additionally, when you open a file for both reading and writing, the writing is usually appended to the end of the file unless you specify otherwise. If you want to overwrite starting at a random point in the file, or from the beginning, then you will need to use file.seek() , and you may wish to look into file.truncate() as well. You can learn more about file object methods here .