python - 更改套接字对象的 __class__ 属性时出现类型错误

Question

有以下服务器代码(我正在定义一个继承自套接字的类，并尝试使用该类调用客户端套接字上的发送方法):

import socket

class LogSocket(socket.socket):
    def send(self, data):
        print("Sending {0} to {1}".format(
            data, self.getpeername()[0]))
        super().send(data)

def respond(client):
    response = input("Enter a value: ")
    client.send(bytes(response, 'utf8'))
    client.close()

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('',2401))
server.listen(1)
try:
    while True:
        client, addr = server.accept()
        client.__class__ = LogSocket
        respond(client)
finally:
    server.close()

客户端代码是:

import socket

client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client.connect(('localhost', 2401))
print("Received: {0}".format(client.recv(1024)))
client.close()

当我运行上面的代码时，服务器崩溃并出现错误:

Traceback (most recent call last):
  File "10_04_server.py", line 20, in <module>
    client.__class__ = LogSocket
TypeError: __class__ assignment: 'LogSocket' object layout differs from 'socket'

这个错误是什么意思？为什么会发生这种情况？

Answer 1

将 __slots__ 属性设置为 ()，这样就可以工作:

class LogSocket(socket.socket):
    __slots__ = ()
    def send(self, data):
        print("Sending {0} to {1}".format(
            data, self.getpeername()[0]))
        super().send(data)

relevant pieces of documentation是:

The action of a __slots__ declaration is limited to the class where it is defined. As a result, subclasses will have a __dict__ unless they also define __slots__ (which must only contain names of any additional slots).

还有

__class__ assignment works only if both classes have the same __slots__.