file operation of python

#! /usr/bin/python 

fn = "a.txt"

fw = open(fn,'w+')

fw.write('aaaa')

fw.readlines()

fw.tell()

fw.close()

#! /usr/bin/python 

fn = "a.txt"

fw = open(fn,'w+')

fw.write('aaaa')

fw.readlines()

fw.tell()

fw.close()