class Client(object):
    cache = None
    db = None
    def __init__(self, hostname="127.0.0.1", port="11211", expiry=900):
        if hostname and port:
            import memcache_client
            self.cache = memcache_client.Client(hostname, port, expiry)
            
        import db_client
        self.db = db_client.Client()
 
    def set(self, key, value):
        """
        This method is used to set a new value
        in the memcache server and the db.
        """
        self.db.set(key, value)
        if self.cache:
            self.cache.set(key, value)
 
    def get(self, key):
        """
        This method is used to retrieve a value
        from the memcache server, if found, else it
        is fetched from db.
        """
        if self.cache:
            v = self.cache.get(key)
            if v is None:
                v = self.db.get(key)
                if v is not None:
                    self.cache.set(key, v)
        else:
            v = self.db.get(key)
        return v