gistfile1.py

class BottomPolicy(Policy):
    """Policy that drops everything."""
    def __init__(self):
        pass

    def get_physical_rep(self, switch_map, port_map):
        return self

    def get_actions(self, packet, loc):
        return []

    def is_bottom(self):
        return True

    def restrict(self, predicate):
        return BottomPolicy()

    def __str__(self):
        return "BottomPolicy"

    def __eq__(self, other):
        return isinstance(other, BottomPolicy)