On the wiki it says that nagini is likely to be either an anaconda or a boa constrictor, this makes no sense because we know that nagini is venemous and neither of those other two snakes are
Here you are:
“Yes, it’s rather funny, really, that next to no one realized the snake that Harry set free in Philosopher’s Stone turned out to be Voldemort’s final Horcrux, Nagini.” —J.K. Rowling
- Where and when exactly did JKR say that? Link or it didn't happen. —The preceding unsigned comment was added by 188.8.131.52 (talk • contribs).
- Horcruxes have their own ways of defending themselves, so it is possible that Nagini was never venomous until after she became a horcrux. It's possible that she is a boa constrictor.—The preceding unsigned comment was added by 184.108.40.206 (talk • contribs).
- Nagini is a reticulated python and I'm 100% sure that it looks exactly like one since I work at a reptile shop. Reticulated pythons are the longest in the world and can grow to 35ft. Where in the movie does it ever say Nagini is venomous? She is a large constrictor.
- It says in the book that she's venomous - that there's something in her venom that keeps Arthur Weasley's wounds from healing properly. Oh, and for the record, per Harry Potter: A Pop-Up Book, the filmmakers' intention was to model Nagini after a Burmese python, though with some creative license, as Rowling described the snake as being much longer than an actual snake of that type. ProfessorTofty 02:17, January 23, 2012 (UTC)
In the 1st book the snake let loose by harry is described as being a Boa Constrictor and considering the sign identified the species' origin as Brazil, it is implied that it is a Common Boa Constrictor (r)
The snake portrayed in the 1st movie could be either a Burmese Python or African Rock Python, as they look almost identical. Because the sign in the movie says the snake is from Asia we can infer that it is a Burmese Python.
I don’t believe Nagini's appearance was ever likened to a particular snake by Rowling, only that it was over 12 feet long. Based on that distinction we can safely presume that she is a type of constrictor, either a boa or python, considering that a King Cobra is the only non-constrictor to average 12 feet or more in length. Though the King Cobra possibility might explain why Nagini might be venomous, there is absolutely no way a cobra could ever swallow even a baby much less a full grown adult human.
In the Goblet of Fire movie Nagini is animated to be a Burmese Python, essentially. In the later movies Nagini is portrayed as being identical to a Reticulated Python.
Given all the information I’ve just given, we are able to come to a few conclusions:
1. Every snake in both the books and the movies are depicted as constrictors.
2. No constrictor is poisonous (in the muggle world at least).
3. No Constrictor has fangs (as described by Rowling).
3. There are only 3 snakes that could even conceivably come close to growing large enough to eat an adult human: Reticulated Python, Burmese Python, and a Green Anaconda (all three of which are constrictors). There has never been a recorded example of any snake swallowing or even being able to swallow an adult human (Shoulders get in the way) and certainly none of these three could even, hypothetically, attempt to do so at 12 feet in length, as described by Rowling.
Armed with these facts one can only conclude that either Nagini is a unique creation of Rowling's mind not based on any real snake or is one of the aforementioned 3 snakes that has had a permanent engorgement charm cast upon it as well as a spell to augment her with poisonous fangs.