python `with .. as ..`语句和多个返回值

Question

我正在尝试使用 python with-statement(又名上下文管理器)来确保 server_socket.accept() 创建的 TCP 连接套接字始终关闭。然而，明显的形式不起作用，因为 accept() 返回多个值。

有没有办法对具有多个返回值的函数使用 with 语句？

下面是一个最小的例子，我想使用类似注释代码的东西来替换 try/finally block 。

#!/usr/bin/env python3

import socket
from socket import socket as Socket

with Socket(socket.AF_INET, socket.SOCK_STREAM) as server_socket:

        server_socket.bind(('', 8011))
        server_socket.listen(1)
        print("server ready")

        while True:

            # with server_socket.accept() as (connection_socket, _):
            #     request = connection_socket.recv(1024).decode('ascii')
            #     reply = request.upper()
            #     connection_socket.send(reply.encode('ascii'))

            try:
                connection_socket, _ = server_socket.accept()
                request = connection_socket.recv(1024).decode('ascii')
                reply = request.upper()
                connection_socket.send(reply.encode('ascii'))

            finally:
                connection_socket.close()

使用带注释的 with 语句时的错误信息是:

Traceback (most recent call last):
  File "./test.py", line 26, in <module>
    with server_socket.accept() as (connection_socket, _):
AttributeError: __exit__

大概这是因为元组没有 with 所需的 __exit__ 属性。

Answer 1

socket.socket 的返回值有一个内置的上下文管理器，它实现了__exit__ 和__enter__。 accept 返回的元组没有，但您可以从元组中分离出客户端套接字和地址，并单独在客户端套接字上使用 with:

import socket

with socket.socket() as s:
    s.bind(('',8000))
    s.listen(1)
    c,a = s.accept(s)
    with c:
        while True:
            data = c.recv(1024)
            if not data: break
            c.sendall(data)