Juveniles can be shy, so it’s best to start them off in smaller enclosures measuring 1 foot long, 1 foot wide and 1 foot tall. Adult green tree pythons make full use of the larger sizes, such as 2-feet-long-by-2-feet-wide-by-2-feet-tall enclosures or 3-feet-long-by-2-feet-wide-by-2-feet-tall enclosures.One of the biggest misconceptions about green tree pythons and arboreal snakes is that their enclosures should be very tall.reen Tree Python Size. Hatchling green tree pythons usually measure between 8 and 10 inches long. Adults average between 4 and 6 feet, with males on the lower end of this scale and females on the upper end.