Depending on where the tank is, a siphon to a drain such as a bathtub may be the easiest. Pythons are okay but waste a lot of water if you use them like a pump and aren't ideal for refilling. As well they are expensive for what you get.
Another alternative is to pump the water out using a small submersible pump with a hose going to drain.
I use separate drain and fill hoses, and have various diameter/size hoses for different tanks. My fill hose has a gooseneck on the end that allows it to hang on the tank and terminates in a tee, so I can fill very quickly if I want. I often have one tank draining while another is filling. In my situation, a Python would be too slow and wasteful of water as well as totally unnecessary.