Rules Engine in C or Python

In your search for RETE based rules engine in Python either Pyke or PyCLIPS could be the one you would want to use.

PS: I had left a comment to S.Lott's answer about Pyke. I have posted a separate answer as per his suggestion and also to let other readers readily know that the rules engine mentioned in this answer could be a probable choice if they are searching for one.

You could look at CLIPS as already suggested or, if you want to pay money or need it Rete2. I've used CLIPS in the past on Unix and sucessfully embedded it into other applications.

Hope this helps.