how fast do burmese pythons grow?

  i want to know how long is she going to be by her 7 month thanks.
It all depends on feeding, but the average Burm is 6 to 8 feet in length at a year of age. Honestly, 3 feet is a little small for a 7 month old, but not horrible. I've seen some that were 4 feet at a year of age and some that were 10 feet. If you feed yours one good meal a week, it should be around 5 foot at 7 months, give or take.
I agree that you need to give it plenty of cage space to start out. they grow fast! if you feed it enough it will out grow a small tank fast. I'd say you need a 40 gallon long aquarium for at least the first year, maybe two years-but it could out grow it in 2 yrs. When it's adult size you need a small room sized cage for it. I'd say 3-4 feet by 7 months sounds right.
with a burmese, i always find it best to put them in the tank they will be in their whole life. they grow extremely fast. yours might be 3 feet by 7 months