I'm currently writing a module for a customer to handle a user's sieve mail filter files. I am required to use python and much to my disappointment I could not find a nice library/package for handling sieve filters.
Question is: Is there something like this?
Milters is a mail filter library, not specifically Sieve. Also, here is an item on the python mailing list asking for people who want to implement RFC 3028 (Sieve language for mail filters). It's dated December 2009 and it doesn't look promising, but there are some ideas there. I think the answer to your question is no.