Do you have a temp probe? Maybe the temperature in the tank is already good. If the cold areas are too cold, you can try insulating the tank by sticking stuff to the sides and partially covering the screen hood with something (if that's what you have). Not too sure about this one but it might help if you put some wood or cloth in the tank. However, I heard pythons need to be kept humid so not sure if that'll cause bacterial/mold issues with the wood/ cloth.
Just on the side, I had to get rid of my under tank heat pad because it was damaging my hog's belly scales (even though I had a temp probe+ thermostat and recommended repticarpet thing over it). So be careful with that