I was recently given my family’s ball python to take care of. We got her when I was 14-15 years old (I’m now 21). She is currently in a 40 gallon enclosure and she eats very well, she just had switched to frozen thawed without issue. I bought a ton of new things for her to make sure she is properly cared for, as my family was not taking proper care of her with the things they had. I can maintain humidity and proper temperatures very well but I have been reading about how a 120 gallon enclosure would be better for her and is the new recommended minimum for adult ball pythons. I want her to thrive and not just survive so I am asking for some advice here. I see sites like petmd saying 40 gallon is good but I also see people on reddit saying 120 gallons is necessary and I am getting conflicting answers everywhere. I trust this place the most so I thought it would be best to ask. Thank you all in advance!
Depends on how big she is - ideally you want a tank that is about as wide as she is long, with enough height to add stuff for her to climb on as your minimum 
For most that would be around a 120gallon (4x2x2) but if she’s smaller than average she could do fine in something smaller, if she’s longer then she’d do better in something larger. I currently have a smaller male in a 3x1.5x2 and he’s doing well but i am thinking of sizing up eventually
Edit: sidenote; remember a lot of people keep these animals in small tub-systems so answers are likely gonna vary widely. My answer is based on my own observations as a keeper rather than a breeder and what ive read in more advanced care groups
I say if she is eating well and even switched from live to ft with no issue, that’s incredible! So imho why rock the boat at this point? Bps can be easily stressed when their environments are completely changed which can do tricks with their eating habits. You can renovate her tank to make it nicer but I would leave it alone at least for awhile….
And yes you are going to get a ton of opinions on the “right” way to house your ball python!
Thank you so much! She is about the same length as the 40 gallon and I definitely want to attempt to upgrade her one day but I don’t want to be a terrible snake owner and limit her. She gets out often for fun times slithering around and hanging out with me and my family (except recently as I got pneumonia and have been waiting for it to clear up, I am no longer contagious though as its been over 48 hours of treatment)
Thank you so much! I definitely don’t want to stress her out and she tends to prefer smaller spaces from what I have observed in the about 7 years we have had her. I did hear that as long as she gets some time outside of the enclosure to move around and stretch often that it can be okay for awhile, which she usually does (until recently as I developed pneumonia even though I am no longer contagious after 48 hours of treatment) so I try really hard to make sure she is as healthy and happy as possible.
Outside of enclosure exercise is always a great thing. If she is getting out a few times a week I think you should not worry about her being in a 40 gal tank. Every situation is different…… 
Than means she has plenty of room to stretch out!
I am so sorry you have been 
ill!
You can always attempt to improve on their care! That’s the best outlook to have really. Just remember that every snake is an individual. Not every snake does well with a change of enclosure.
Because this is a recent change of pace for her, I would keep things the same for a while longer. That way you can ID a lot of her normal behaviors now that you can spend more time with her.
If you do try the 120, give her a couple of weeks to settle in and see how she does, but if she shows any bad stress behaviors like striking at anything that moves or active defensive perching at the tallest points and ready to strike them I would move her back to the smaller enclosure that she obviously felt more comfortable in.
Sometimes the move can make them skip meals a bit. That’s normal, but if she is really refusing food and dropping a good amount of weight then that would also be a sign for me to move her back.
Thank you so much! Doing my best to heal for her to get more outside of the enclosure time!
Thank you so much! I just get nervous with trying to be my best and do my best for her. I appreciate everything everyone has said to me in this thread!