If you only play occasionally, it's very easy to be surprised by changes. The NPCs have gradually been getting tougher and smarter from release to release - if you play regularly, then it's not that noticeable (and they're still no match for a fully-upgraded player ship) ... but if you only play occasionally (so you're also out of practice!) they can be surprisingly dangerous. Assassination missions are one of the more dangerous combat opponents, too.So please, if you have ANY good and helpful advice for me, please share... I really want to be start playing again....
I'd recommend switching to a cheap combat ship - Viper III or IV - to get back into practice. In something like a non-Hazardous RES, there's plenty of police around to help you out, and if you do lose it the rebuy is much smaller. Practicisng your pip allocation is one of the most important things you can get right - 4 to systems makes your shields much more resistant to damage ... but doesn't leave you much for engines or weapons, so switching them back and forth as needed makes you much tougher and effective in a fight.
You can also use a Viper for doing the data delivery missions for an easy extra payout as you move around looking for good bounty hunting sites.
As others have said, 5 million rebuy implies that your Python is not fully upgraded. It *can* be a decent combat ship, but a half-upgraded one is very often a slow and easy target.
(Alternatively, go exploring for a bit - payouts are decent, it's generally safe, and if you don't pick up cargo the pirates will ignore you - and get some rebuys back)