def all(s):
   "Return true if all elements in an iterable sequence are true."
   for x in s:
      if not x:
         return False
   return True

def any(s):
   "Return true if any element in an iterable sequence is true."
   for x in s:
      if x:
         return True
   return False

class Cache:
   """
   Creates a functor that caches the output of a function.
   e.g.
      image_load = Cache(pygame.image.load)
      ball1 = image_load("ball.png")
      ball2 = image_load("ball.png")   # ball.png only loaded from disk once
   """
   def __init__(self, func):
      self.store = {}
      self.func  = func

   def __call__(self, key):
      try:
         return self.store[key]
      except KeyError:
         self.store[key] = self.func(key)
         return self.store[key]