[Tutor] flag to call methods on objects?

[prasad rao]

hello
    I wanted to prevent other users of my computers to read my files.
So tried to creat a module to achieve it.
I used a flag to deside which methods to be called on the object.
somehow it is not working.I realise after 2 days of struggle that
as  it is usuel , I am blind to my faults.
I tested all the metheds except main() in idle interactively,found them
working.
So there is a bug in the main(), kan anyone point it out to me?

<code>


#! usr/bin/env python

import ast,random,os,zlib,string
key=5
class Cripto(object):
    def __init__(self,afile):
        self.afile=afile
    def __digi(self,astring):
        y=[]
        for x in astring:
            y.append(ord(x))
        y=str(y)

        return y
    def __undigi(self,astring):

        alist=ast.literal_eval(astring)
        y=[]
        for x in alist:
            y.append(chr(x))
        astring=''.join(y)
        return astring
    def __gen_string(self):
        s=''
 nl=random.sample(string.ascii_letters,key)
 for x in nl:s+=x
 return s

    def __lengthen(self,astring):
         s=list(astring)
  ns=''
  for x in s:
  ns+=x
  ns+=gen_string()
  return ns
    def __shorten(self,astring):

         s=list(astring)
  ns=''
  for x in range(0,len(s),key+1):
  ns+=s[x]
  return ns
    def __compress(self,astring):
        astring=zlib.compress(astring)
        return astring
    def __decompress(self,astring):
        astring=zlib.decompress(astring)
        return astring
    def main(self):
        sorce=open(self.afile,'r')
        data=(sorce.readlines())
        dest=open ((os.path.split(self.afile)[0]+os.sep+'temp'),'w')
        if data[:1]=='flag1\n':
            ns='flag0\n'
            data=data[1:]
            for line in data:
               nl=__compress((__digi(__lengthen(line.strip()))))+'\n'
               ns+=nl
            dest.write(ns)
        elif data[:1]=='flag0\n':
            ns='flag1\n'
            data=data[1:]
            for line in data:
                nl=__decompress((__undigi(__shorten(line.strip()))))+'\n'
                ns+=nl
            dest.write(ns)

        sorce.close()
        dest.close()

        os.remove(self.afile)
        os.rename((os.path.split(self.afile)[0]+os.sep+'temp'),self.afile)


#========
a=Cripto('C:/pp.txt')
a.main()


<\code>
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