Populates all classes with "altitude", measured as the number of lines from the bottom of the file. And the very useful "fly" function

antigravity.py

import inspect

class GravitationalError(Exception):
    pass

class Fly(object):

    def __get__(self, instance=None, owner=None):
        def fly(*args, **kwargs):
            alt_str = "Flying at the height of %d lines. " % owner.altitude
            members = inspect.getmodule(owner).__dict__.values()
            lst = [(m, m.altitude) for m in members if inspect.isclass(m)]
            pos_str = "All alone here"
            if len(lst) > 1:
                ordered = [x[0] for x in sorted(lst,key=lambda x: x[1])]
                pos = ordered.index(owner)
                if pos == 0:
                    pos_str = 'At the very bottom, below the "%s"' % \
                            ordered[pos+1].__name__
                elif pos == len(ordered)-1:
                    pos_str = 'At the very top, above the "%s"' % \
                            ordered[pos-1].__name__
                else:
                    pos_str = 'Between "%s" and "%s"' %\
                            (ordered[pos-1].__name__, ordered[pos+1].__name__)
            return alt_str + pos_str + ". It's all Python! (http://xkcd.com/353/)" 
        return fly 

class Altitude(object):

    def __get__(self, instance=None, owner=None):
        height = len(inspect.getsourcelines(inspect.getmodule(owner))[0])
        return height - inspect.getsourcelines(owner)[1]

    def __set__(self, instance, value):
        raise GravitationalError("This is not how you're supposed to fly")

def levitate_all():
    frame_globals = inspect.currentframe().f_back.f_back.f_globals
    for cls in [val for val in frame_globals.values() if inspect.isclass(val)]: 
        cls.fly = Fly()
        cls.altitude = Altitude()

levitate_all()