# L-17 MCS 260 Fri 19 Feb 2010 : replace word

# This program replaces each occurrence
# of 'the' by 'one' in a text.

def add_to_buffer(b,c):
   """
   Adds c to a 3-letter buffer b,
   on return is the updated buffer.
   """
   B = b
   if len(b) == 3:
      (B[0],B[1],B[2]) = (B[1],B[2],c)
   else:
      B.append(c)
   return B

search = ['t','h','e']
buffer = []
name = raw_input('give file name : ')
file = open(name,'r+')
while True:
   c = file.read(1)
   if c == '': break
   buffer = add_to_buffer(buffer,c)
   if buffer == search:
      cursor = file.tell()
      file.seek(-3,1)
      file.write('one')
file.close()