Proper size tub for young BP?

Hi everyone. I'm looking to get a young ball python at a reptile expo in my area. This will be my first. I have a 19.5 qt rubber maid tub, dimensions 16"×11"×9". Is this a good size for a young python? I'm worried that it has too much height and not enough floor space.
Also, when he's a bit bigger, what size tub should I upgrade him to? Thank you for your help :-)

Depends on size and age. My 4 month old ball python Is housed In a 15qt, he'll stay In there until he's about 350-500 grams.

Thanks! I won't have him until October, but I'm guessing he'll only be a couple months. Do you know the dimensions in inches of the 15qts?