This post will be too late if you've received a 3 day eviction notice. Will share my thoughts anyway.
Many cities have strict, but unenforced, ordinances regarding pets. One example I researched was Plano, TX. There is a city ordinance forbidding private ownership of all herps. Period. After reading the law I called animal control and they confirmed my understanding of it. I then called 3 local vets who advertise as herp specialists. Only one of them knew about the law. I called the local PetCo's (there are 2 in Plano). They both sell herps, including boas and pythons. No one at either store had ever heard of the law.
Bottom line? All it takes is one call. A landlord, ex-girlfriend, pissed off neighbor, whatever. Animal control shows up and your herps are gone. This almost never happens, but be aware of the risk.
Regarding your lease: these nearly always have an "integration clause" which says essentially that the entire agreement is in the written lease. This excludes oral understandings from being incorporated into the agreement. Basically, the landlord could say "snakes are fine" but if the written lease says "no animals" then you are in breach. The landlord is a lying SOB, but you are still in breach.
A three day eviction notice allows you to "cure" so if you get rid of the snakes within three days of being served then you can't be evicted (at least for that).
There are other arguments to make: the eviction is unfairly punitive, laches, etc. You'd need a lawyer to make them for you.