Diamonds are cool climate pythons and shouldn't be over heated, but they also need some heat to digest their food (i wouldn't exceed 29 degrees but some might offer other opinions).
I keep my diamond in a large exo terra tank with a heat mat under one corner of it, that is thermostat controlled to 29 degrees Celsius, for about 5 or 6 hours a day. The rest of the day the enclosure is at ambient room temperature.
Glass is a good choice for a diamond given their unique keeping requirements, and the heat from the heat mat also passes through glass a lot easier than through plastic...
But i live in Sydney which is their natural climate. Which part of the country are you in?