I've actually used a wet/dry vac in the past... (Rigid brand for me)
Remove all filters.. Turn it on.. ..stick tube in water....suck....It will stop itself when the tank is full (ball inside seals inlet causing drastic noise change/loss of suction)... Dump tank..
Works great for getting down in your sump too if its low on the floor where you can't easily start a siphon..
Before that I've always just used tubing (like 1/2" ID or so) and sucked on the end to start a siphon and voila.. Either run the outlet into a 5G bucket or down the drain if close,etc...
But I have seen the python stuff and it really works great too.. My only complaint was that you are wasting good water while its running..
A pump will work just fine too.. BUT you can clog/ruin it if you are sucking sand/cyano/algae,etc... and they typically aren't self priming so you need to put the tank in the water and can't just use an external pump with a tube on the inlet (unless you put it into the tank or get a self priming pump and they are typically large/bulky)
The pump to me would be my last choice..
I'm a super fan of the wet/dry vacs now.. They work fantastic..
You can even add a valve to the tank and have it draining out all the time for endless water change capability.. or just to make it easier to drain..