Can I mark variables as transient so they won't be pickled?

Let's say I have a class:

class Thing(object):
    cachedBar = None

    def __init__(self, foo):
        self.foo = foo

    def bar(self):
        if not self.cachedBar:
            self.cachedBar = doSomeIntenseCalculation()
        return self.cachedBar

To get bar some intense calculation, so I cache it in memory to speed things up.

However, when I pickle one of these classes I don't want cachedBar to be pickled.

Can I mark cachedBar as volatile / transient / not picklable?