class MultiMapping: def __init__(self, *stores): self.stores = list(stores) self.stores.reverse() def __getitem__(self, key): for store in self.stores: if store.has_key(key): return store[key] raise KeyError, key def __setitem__(self, key, val): self.stores[0][key] = val _marker = [] def get(self, key, default=_marker): for store in self.stores: if store.has_key(key): return store[key] if default is self._marker: raise KeyError, key return default def __len__(self): return len(self.items()) def has_key(self, key): for store in self.stores: if store.has_key(key): return 1 return 0 def push(self, store): self.stores = [store] + self.stores def pop(self): if not len(self.stores): return None store, self.stores = self.stores[0], self.stores[1:] return store def keys(self): return [ _[0] for _ in self.items() ] def values(self): return [ _[1] for _ in self.items() ] def copy(self): copy = MultiMapping() copy.stores = [_.copy() for _ in self.stores] return copy def items(self): l = [] seen = {} for store in self.stores: for k, v in store.items(): if not seen.has_key(k): l.append((k, v)) seen[k] = 1 return l