import bz2

f1 = bz2.BZ2File(r'file.txt.bz2', 'r')
f2 = open(r'file.txt', 'r')
lines = 0
while True:
   line1 = f1.readline()
   line2 = f2.readline()
   if line1 == '':
      break
   lines += 1
   if line1 != line2:
      print 'line number: %d' % lines
      print repr(line1)
      print repr(line2)
f1.close()
f2.close()