Yes some , not alot gets sucked into the python. I swirl the the vac around about and inch above the sand and all the **** comes up and the vac sucks it up!
Just put some Malaysian Trumpet Snails (Melanoides Tuberculata) in your tank. Don't worry, they won't bother you, you'll never see them, they live in the sand. They keep the substrate free of organic matter, and they aerate it doing so. No tank should be without them! I have sand, and I don't even have to vacuum. My filter & snails clean the tank for me. Of course, you will have some loss of sand when you hold the hose straight into it during water changes, but that is avoidable.
for me sand is a lot easier to clean that other subtrates. although you will have different grade of sand. the very fine sand will get sucked up like crazy so you have to be careful in siphoning on top of it. the larger the grade the easier the cleaning.
I use tahitian moon sand its not too bad, you can get pretty close w/o sucking any up.
Heres something I figured out :you dont have to worry about this though, if you get a small bucket like 2.5 gallon and stick in under your python in the sink. You can suck up as much sand as you want . the bucket will catch all the sand but the dirty water and crap will flow over the top of the bucket. Than when your done you can scoop out the sand and dump it back into the tank. No sand lost or sand down your drain.
my snails are not taking over. A snail problem is often a problem of overfeeding your fish, which I don't do. My corydoras eat what's leftover. The trumpet snails sometimes come to the top water level at night, so it'd be easy to remove a few around midnight. I never do that, though. That nightly migration seems to be periodic. I couldn't make out a pattern... Anyhow, trumpets rock! I can only encourage you to introduce them in your tank.
When it comes to cleaning sand. I've learned (IMO) that it is a pain in the @$$. You can't just vaccuum through it. You have to hover just at the surface and/or stir it up and catch the debris while it floats in the water.