Decorative dispatch table

decorative_case.py

class Dispatcher(object):
    def __init__(self):
        self.table = {}

    def choice(self, key=None):
        def decorator(fn):
            self.table[key or fn.func_name] = fn 
            decorated_fn = fn
            return decorated_fn
        return decorator

    def otherwise(self, *a, **b):
        return self.choice('__otherwise__', *a, **b)

    def case(self, key, *a, **b):
        if key in self.table:
            self.table[key](*a, **b)
        else:
            self.table['__otherwise__'](*a, **b)

d = Dispatcher()

@d.choice(key="hot")
def steamy(x, y=3):
    print "so hot", x, y

@d.choice()
def cold(x, y=3):
    print "cold", x, y

@d.otherwise()
def huh(x, y=-3):
    print "huh?", x, y

d.case("cold", 1)
d.case("hot", 2)
d.case("tepid", 3, y=7)

decorative_dictionary_walker.py

class DictionaryWalker(Dispatcher):
    def walk(self, parent):
        other_fn = self.table.get('__otherwise__', None)
        for key, child in parent.iteritems():
            if key in self.table:
                self.case(key, parent, key, child)
            elif other_fn:
                other_fn(parent, key, child)

dw = DictionaryWalker()

@dw.choice("left")
def walk_left(p, k, c):
   print "left:", c

@dw.choice("right")
def walk_right(p, k, c):
   print "right:", c

@dw.otherwise()
def huh2(p, k, c):
    print "unexpected key", k, ":", c

dw.walk(dict(left="weak", head="big head", right="strong"))