#!/usr/bin/python
import sys
import re
if __name__=="__main__":
 f=file("hi.txt","w+")
 li=["hello/n","hi/n"]
 f.writelines(li)
 f.close()

#!/usr/bin/python

import sys,os

f=open('hi.txt','r+')
flist=f.readlines()
flist[4]='hi/n'
f=open('hi.txt','w+')
f.writelines(flist)