In couchdb-python the db.save(doc)
method returns tuple of _id and _rev. You're using couch-query - a bit different project that also has a db.save(doc) method, but it returns a different result. So your code should look like this:
def updateDoc(self, id, json):
doc = self.db.get(id)
doc["firstName"] = json["firstName"]
doc = self.db.save(doc)
print doc['_id'], doc['_rev']
print "Saved"