I have a male woma. Can't imagine him being in anything less than a 4 x 2. Females will definitely at minimum need a 4 x 2, bigger for larger females. And they are active, not like a corn but nothing like a couch potato ball python. Mine explores, he uses all 5 of his hides (they are mainly there for stimulation) and would pick a random one to use every other day. Mine is almost never found curled up, stretched out and will use the space given.
I just purchased a 40 gallon tank today for my growing corn. He is in there temporary until I see his full grown size so I can either upgrade or make it permanent. In your case, if you pick up a small adult colubrid, like a small corn or a gray banded king, that could work. Humidity is not a concern, and they don't seem too bothered being in a glass tank. Some boas and pythons can be shy eaters, like dumerils boa, where a glass tank may be at first intimidating to them.
I also have a Children Python. I would recommend that for the 40g tank, but make sure to add plenty of climbing material. These snakes are a good size, but exploring is not so common as much as they just want to eat, a lot. The only time I see my Bender out of his hide perked on his drift wood is food, which is 99% of the time. Same spot. Every day. Not really paying attention to other things. The 1% is when he is in shed, he hides for days. So colubrids would be more entertaining to watch.