1.python什么是聊天弱引用,__weakref__如何使用?
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python什么是弱引用,__weakref__如何使用?
大家好,我是室源程序员老王。让我们来谈谈Python中的源聊弱引用。
假设我们需要创建一个匿名聊天室。天程为了实现这一目标,聊天我们首先定义了一个代表用户的室源npm install 本地源码类User。由于匿名聊天,源聊用户无需注册,天程为每个用户分配一个唯一的聊天id。我们确保id的室源独特性,通过维护一个全局字典,源聊存储当前所有id与用户之间的天程关系,一旦发生冲突,聊天重新生成id并更新全局字典。室源
随后,源聊我们定义了聊天室函数chat_room,该函数允许多人参与聊天。在聊天结束后,这些匿名用户将失去作用。然而,问题在于,剑指标源码当用户被创建时,全局字典id_user中将记录所有User实例的引用。即使chat_room返回,id_user仍保有所有User的引用,导致这些实例无法被垃圾回收,进而影响id的重用。
解决这个问题的一种方法是,在chat_room返回前从id_user中删除用户引用。但考虑到实际聊天室功能的复杂性以及可能的异常处理,选择正确的矩阵键盘源码del id_user的位置需要谨慎。此外,这种操作在逻辑上并不连贯,易于引入错误。
引入弱引用提供了一种替代解决方案。Python的weakref库中的WeakValueDictionary可以作为替代id_user的普通字典。这个WeakValueDictionary实现了字典接口,但其特殊之处在于,它的值为弱引用。
强引用,如chat_room中的it监控源码u1和u2,只要对象还存在强引用,它们将不会被垃圾回收。因此,u1和u2指向的User实例在chat_room中不会被回收。然而,弱引用不同,如id_user中的值。虽然它们同样指向User实例,但只要实例没有其他强引用,这些User将被回收,汉风西游源码并且id_user中对应的条目也会被删除。因此,当chat_room返回时,u1和u2指向的User已无强引用,id_user会自动执行删除操作,无需显式调用del。
输出结果显示,尽管我们没有删除id_user中的元素,id_user仍然为空,符合预期。如果全局变量中已有一个User,再次运行程序,id_user将保留一个User,因为全局变量u一直引用着这个User。
除了WeakValueDictionary,还有WeakKeyDictionary和WeakSet。WeakKeyDictionary中Key为弱引用,而WeakSet相当于只有Key没有Value的WeakKeyDictionary。更多细节在这里就不赘述。
ref类允许我们创建一个简单的弱引用。例如,我们可以对全局的User u创建一个ref类的实例。当我们调用u_ref()时,ref类会返回u对应的强引用。如果在调用u_ref()之前,User的强引用已经消失,再次调用u_ref()将返回None。
最后要指出,并非所有对象都支持弱引用。例如,数字和字符串不支持弱引用。考虑到这些类型在计算中可能重复出现,将其弱引用可能不符合逻辑。相比之下,类的实例、容器等对象更适合使用弱引用。完整的可弱引用的对象列表在文档中提供,但在实际使用中,无需特意查阅。
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self.set_reuse_addr()
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"""
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pass
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"""
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def __init__(self, server, sock):
async_chat.__init__(self, sock)
self.server = server
self.set_terminator('\n')
self.data = []
self.name = None
self.enter(LoginRoom(server))
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try:
cur = self.room
except AttributeError:
pass
else:
cur.remove(self)
self.room = room
room.add(self)
def collect_incoming_data(self, data):
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self.data.append(data)
def found_terminator(self):
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line = ''.join(self.data)
self.data = []
try:
self.room.handle(self, line)
except EndSession:
self.handle_close()
def handle_close(self):
async_chat.handle_close(self)
self.enter(LogoutRoom(self.server))
class ChatServer(dispatcher):
"""
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"""
def __init__(self, port):
dispatcher.__init__(self)
self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
self.set_reuse_addr()
self.bind(('', port))
self.listen(5)
self.users = { }
self.main_room = ChatRoom(self)
def handle_accept(self):
conn, addr = self.accept()
ChatSession(self, conn)
if __name__ == '__main__':
s = ChatServer(PORT)
try:
asyncore.loop()
except KeyboardInterrupt:
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