When it comes to larger objects, snakes are very hit and run. Rattlesnakes in particular coil and warn whatever is treading in its area to stay away. If the snake is instigated enough to attack it will immediately flee if it has the option too. So unless you manage to step into a nest of them.. you don't have to get away from the snake because it's already fleeing.
Water moccosines are the exceptions. Those *** are aggressive and will attack without provoking them. Stay out of swamps.