Okay, to begin with a safety note. Heat lamps are a fire hazard and have been known to explode and catch fire. I advise against them if at all possible. 

If you do get one, it does not have to be a UVA/UVB bulb. Ball pythons are nocturnal and don't need it. It should be placed on one side of the tank to create a temperature variant. Putting it over the water is not a bad idea if you have low humidity. Ball pythons tend to need some humidity to shed all in one piece. I wouldn't recommend getting anything stronger than a 40-60W bulb for your tank, depending on size and height of the tank. The higher it is, the stronger the wattage needs to be. The larger the tank, the stronger the wattage needs to be. I have always used the "night" lamps that are red. Even if just during the day. I liked the look and they tend to provide more heat. MOST IMPORTANT though, is your temperatures that you are maintaining. Basking spot should be right around 90 with the cool side around 80. Be 100% sure about your temps. Get a temp gun if you need to. Husbandry is the MOST important part of keeping herps. They can become sick if you don't house them correctly. 

Good info...and if I get what you're saying--the bulb you use even during the day is red? How would you ensure a consistent temp. though? Would you play with the distance of the bulb from the tank/enclosure? And being nocturnal...should I have the light on at night?  Or if I had a basking light--would they bask during the day? 

Thanks!

P.S.  Also...it just now occured to me as I re-read--if you advise against them...what are the other heating options? I heard that heat rocks are bad?

First of all and most urgent do NOT put a heat light over a 7 gallon tank. You will cook your snake. 

I disagree with heat lamps being a fire hazard and in 8 years have never had one explode. I will go on to say any thing you plug in can potentially be a fire hazard. The best set up for having both a heat light and an under tank heater is a 20 long. You can find used ones on craigslist, at thrift stores or save up about $50 to get a new one.

In my opinion ceramic heat emitters are not well recommended for ball pythons because they suck out the humidity. A 60 watt red bulb that is not a spot is all you should need, unless your house drops into the 40's or you get a bigger tank. The humidity hide is a good idea but keeping it wet and him spending all of his time in it is a recipe for sale rot. 

I don't know how thick your bedding is but here is what I suggest. If you can, just go get the bigger tank, yes he is small now but a 20 long will hold him forever. You can add a few extra hides and remove them as he gets bigger. If you can't get one yet, then make sure there is only about a 1/2 inch of bedding covering the heat pad and move his humid box so he can lay on the warm bedding with out being in the box. Maybe even take it out, mist him daily and give him the box when he goes into shed. 

Check the temps just above the heat pad on top of the bedding because that is where he is and where the temp matters. You can lay one of those round thermometers they sell cheap at pet stores on top of the bedding for a few minutes to get an idea of the temp. 

p.s. Heat rocks should be outlawed they are worse than bad.

To specifically address your questions, no you do not need a dual fixture. They do not need uv or a night basking lamp. Blue lamps give off more light and add less heat than red lights. They are used for different lizards or chameleons mostly. Once you get a larger enclosure whether you buy or build, the heat light should go over the same end as the pad. In the wild ball pythons will find a place to bask, like a rock thats been in the sun, where heat comes from above and below. They are diurnal but  come out more at night because that is when their prey is more active. But they eat and then go back to bed. The heat light can sit on top of the screen top on a glass tank (20 long) or if you put it inside a built enclosure make sure it is well screened far enough out from the bulb itself and very secure.