You must practice Tesla-jitsu, which translate to "way of the unarmed egress"... I normally don't give lessons via forum posts, but since I am a black belt in Tesla-jitsu, I shall teach you "the way" grasshopper.
1) Clear your mind as you approach the assailant(parking space), use a fake seat setting that lowers your seat, and positions the steering wheel high and forward, also when possible, set the suspension to the highest level if it is a commonly used space
2) after putting the car in park, take your right foot off the brake and put it on the sloped part of the floor behind the brake, next grab the top of the steering wheel with your right hand while simultaneously unbuckling your seat belt with your left hand reaching across your body
3) next in a quick motion, shove the door open with your left hand, to the point wide it will stay open without holding the door
4) next, press your neck and shoulders into the seat while pressing down with your right foot and simultaneously lifting your left leg out of the car, don't reach your foot, but rather imagine you are trying sticking your left leg out while allowing your hips to turn under you (as though you are trying to keep your butt off the seat), while keeping your left leg under you so that when you sit back down, you are positioned on your left butt/hip with right hand on steering wheel and left hand on the outside of the car on the pillar
5) now, in one graceful motion, pull your upper body out of the car first and in one smooth motion, stand up on your left foot.
When done properly, you will look very cool and only break two ribs with this maneuver ... seriously though, it does work (a friend of mine who drives what gaijin refer to as a "sports-a-car-u" showed this move to me)
To get into the car, reverse the steps...
Be aware grasshopper that if you do this in the UK, you may be arrested for sexual assault when you climb into your passenger's lap... for the driver's side, is on the right side of the car