zlib and gzip

[Greg Bakken]

I am writing a python program that recieves 'compressed and encoded'
strings from another piece of software.  I can successfully uncompress
and decode the strings via

import base64, zlib
def getString(s):
  s = base64.decodestring(s)
  s = zlib.decompress(s, -15)
  return s

Now, I want to take a 'readable' text string, and compress and encode
it the same way as the other piece of software.  I first tried the
seemingly obvious (but incorrect)

import base64, zlib
def makeString(s):
  s = zlib.compress(s, 9)
  s = base64.encodestring(s)
  return s

I have also tried using the gzip module to do this like

import base64, gzip, StringIO
def makeString(s):
  sio = StringIO.StringIO()
  gzipper = gzip.GzipFile(mode="wb", fileobj=sio)
  gzipper.write(s)
  s = base64.encodestring(sio.getvalue())
  return s

What I would like to be able to do is take a string s, pass it through
the makeString function, and pass the result through the getString
function, and end up with the original string s back.  I have to stick
with the way getString is, so I can handle strings from another
program, so I need to adapt makeString accordingly, but cannot figure
out how.

Greg