table = set([])
class GlobeLearningTable(object):
def __init__(self,mac,port,dpid):
self.mac = mac
self.port = port
self.dpid = dpid
def add(self):
global table
if self not in table:
table.add(self)
class LearningSwitch(object):
def __init__ (self, connection, transparent):
self.connection = connection
self.transparent = transparent
self.macToPort = {}
connection.addListeners(self)
self.hold_down_expired = _flood_delay == 0
def _handle_PacketIn (self, event):
packet = event.parsed
self.macToPort[packet.src] = event.port # 1
packet_src = str(packet.src)
packet_mac = packet_src.upper()
entry = GlobeLearningTable(packet_mac, event.port, dpid_to_str(self.connection.dpid))
entry.add()
问题：entry.add()方法每次调用时都会添加新对象，并增加表中的项目。
这不应该发生，因为
帮助：这种设置有什么办法，我只能在对象不在表中时添加它。
您需要实现__eq__和__hash__方法来教Python如何识别唯一GlobeLearningTable实例。
class GlobeLearningTable(object):
def __init__(self,mac,port,dpid):
self.mac = mac
self.port = port
self.dpid = dpid
def __hash__(self):
return hash((self.mac, self.port, self.dpid))
def __eq__(self, other):
if not isinstance(other, type(self)): return NotImplemented
return self.mac == other.mac and self.port == other.port and self.dpid == other.dpid
现在，您的对象是可比较的，相等的对象也将返回相等的值__hash__。这让set和dict对象有效地存储你的对象，并检测它是否已经存在：
>>> demo = set([GlobeLearningTable('a', 10, 'b')])
>>> GlobeLearningTable('a', 10, 'b') in demo
True
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