Yes, it is illegal to sell ball pythons (Python regius) in New York City.
New York City Health Code §161.01 (Wild Animals) prohibits the sale, possession, or harboring of all non-human primates, wild felines, wild canines, bears, venomous reptiles, crocodilians, and all other snakes — including non-venomous constrictors like ball pythons.
Legal in most of New York State (outside the 5 boroughs) with standard reptile permits — but check local county/municipal laws (e.g., Westchester, Suffolk, Nassau have restrictions).
Public safety (escapes, bites, salmonella), animal welfare (impulse buys, improper care), and environmental risk (released pets — though ball pythons unlikely to survive NY winters).
If you live in NYC and want a reptile: Consider leopard geckos, bearded dragons, corn snakes (check local legality), or turtles/tortoises — but verify each species against §161.01.