Last night I did something similar, took a mining contract over 3 units of Methanol Monohydrate Crystals (what a bulky term!) but didn't want to take my Python for various reasons (not taking a sledgehammer to crack a nut only being one of them) and took my Cobra Mk3 instead. At some point on my way back I was interdicted and since I'm allied with all factions in this system there was immediately a security ship at hand. The 2 vs one was doable, even with my limited Mining Cobra (2x class 2 gimballed lasers) and got me a nice 40k bounty.
That's the crux with mining, you basically fly ships that are horribly crippled for combat, even worse than trading ships: You want one or better two mining lasers, cargo space and limpet controllers. In other words, if you still want to fight with such a ship you need to pick both your opponents and situations *very* carefully. Otherwise your only options would be running.
You can always join one PP faction (I forget which one) and stick with them for a month to get the Mining lance, which is a fixed small mining/beam laser combo. I use a pair of those on my Mining Asp.