15/16qt tubs will hold most ball pythons till they are around 700 grams,
although I prefer to move them into large tubs around 500 grams.
One UTH plugged into a thermostat to keep it at 90-92 degrees will sufficiently heat the cool end of the tub in a room with an ambient temperature of 75 degrees.
I use flexwatt heat pads wired into a plug in and plugged into a thermostat.
Flexwatt is $3.60 for 11 inch wide x12 inch long piece that can be cut to any length.
Premade UTH's can set you back over $20 and flexwatt does the same thing
Even after shipping priority flexwatt is much cheaper than premade UTH's.
Don't forget a probed thermometer for reading your temperatures on the cool end and on the hot spot, accurite is a decent one and only around 12 bucks.