Personally, I wouldn't keep anything larger than a hatchling in a tub that small... All of my 2016 Bloods and Short Tails went right into 28 qt. racks, which is probably a little too large, but the excess space is consumed with wadded up newspaper for them to hide under, a hide and a large water dish and they have been doing great. If you are only going to keep him in there for a month he should be alright, though...

In my opinion that size tub is also way too small for a Ball Python that size. As a general rule, if the snake can stretch all the way down the long side + all the way along the short side it is too small, but I feel that is even pushing it. Going by the dimensions you gave that would only be 24" total for a 30" snake...