What tank was it that you hadn't performed a water change in 7 months on? I wouldn't perform a large wc on that one at first because there's no telling what the TDS levels are and a sudden change in TDS levels can cause osmotic shock in fish.
Your bacteria in your biofilter might not have survived in that tank if the pH has gone too low. With my water (very soft, less than 2dKH, 2dGH) if I go only 3 weeks without a wc on one of my cichlid tanks the nitric acid eats at the KH reducing it to 0 and the pH will begin to crash. I once measured the pH with a pretty reliable meter at 5.6 after ~3 weeks. Check your ammonia and nitrite in that tank especially after a wc.
The python will make water changes so much easier and the easier they are to do the more likely you'll be to do them. I don't know to what extent it might reinvigorate your interest in fishkeeping though. I'd definitely wait and see how that works out before getting any new fish. If you end up taking care of the fish you have now and perform regular WCs then you might consider getting something like a cichlid.