I was trading in the Type 7 making more than 1 million an hour. The python was finally going to be my jack of all trades ship to allow me to do the grinding and tidious trading and to later relax doing some bounty hunting near a resource extraction point in the rings of a planet. Lo' and behold, after purchasing the Python, the upgrades were very expensive (as expected and calculated prior to buying it), but the cost to refuel and repair the ship eventually led to bankrupcy and now I'm forced to use my last money I have to buy a hauler and start over from the beginning. I still have a Python parked in a space port somewhere, but I am not going to be able to use it or fly it because the insane refuel cost that I just can't uphold in it.
If you are looking to purchasing a Python, going from a Type 7 or Imperial Clipper, make sure you have at least 56 + 80 Million credits before you buy the ship. Don't trade your Type 7 in for it, don't sell your other ships, just buy the Python when you still have your other ships. You might need the Type 7 in order to grind the credits you need to be able to just fly.
The only one line on the wikipedia about the Python was: "the Python does suffer from exceptionally high operating costs, making it a potentially cost-prohibitive option for many pilots.".
The real truth is that it costs 16 000 to refuel 10%. Which means it costs 5000 CR per ton of fuel to drive. So unless you have a lot of money to do the big 200+ tons of trading ready, you will go bankrupt trying to fly this ship.