graph-like structure in redis

gistfile1.py

class Isred(Redis):
  def node(self, serial = None):
    return Node(self, serial)

class Node(dict):
  def __init__(self, r, serial = None):
    self.redis = r
    self.serial = str(serial) if serial else r.incr('serial')

  def __getitem__(self, key):
    return self.redis.hget('attr-%s' % key, self.serial)

  def __setitem__(self, key, value):
    return self.redis.hset('attr-%s' % key, self.serial, value)

  def delete(self):
    raise Exception('you should extend the base class' 
      ' to determine what attributes is to be deleted')

  def link(self, target, self_type = '', target_type = ''):
    self._link(self, self_type, target)
    self._link(target, target_type, self)

  def _link(self, node, link_type, target):
    links_key = ('link-%s' % link_type) if link_type else 'link'
    links = self.redis.hget(links_key, node.serial)
    if links:
      links = set(links.split())
      links.add(str(target.serial))
    else:
      links = set([str(target.serial)])
    self.redis.hset(links_key, node.serial, ' '.join(links))

  def get_links(self, link_type = ''):
    links_key = ('link-%s' % link_type) if link_type else 'link'
    links = self.redis.hget(links_key, self.serial)
    return links.split() if links else []

  def is_link_to(self, target, link_type = ''):
    return target.serial in self.get_links(link_type)