You cannot decode an md5 hash, as hashing is a process that is best thought of as one-way encoding (that is to say what is hashed cannot be de-hashed; one can only determine what was hashed, either by examining a list of known hashes, or by hashing a set of inputs and matching the resulting hashes with the hash you are trying to "decode").
Quoting Wikipedia, the key features of such a hashing algorithm are:
it is infeasible to find a message
that has a given hash,
it is
infeasible to modify a message without
changing its hash,
it is infeasible to
find two different messages with the
same hash.
The most common uses of such algorithms today are:
- Storing passwords
- Verifying the contents of files.
If you want to two-way encrypt the data, you need to look at other cryptographic libraries for Python (As usual, Stackoverflow has a recommendation).