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当您从python对象抛出异常时,它会发生什么情况

sockets garbage-collection exception python

bstpierre Edgar Aviles · 技术社区 · 15 年前

当它“卡住”时,netstat显示两个连接到端口的套接字。服务器正在等待来自第一个套接字的输入,但是它还没有处理新的套接字。

我在一个虚拟服务器上运行此操作,该虚拟服务器对每一条传入线路都回复“error\n”。

import socket

class MyException(Exception):
    pass

class MyClient(object):

    def __init__(self, port):
        self.sock = socket.create_connection(('localhost', port))
        self.sockfile = self.sock.makefile()

    def do_stuff(self):
        self._send("do_stuff\n")
        response = self._receive()
        if response != "ok\n":
            raise MyException()
        return response

    def _send(self, cmd):
        self.sockfile.write(cmd)
        self.sockfile.flush()

    def _receive(self):
        return self.sockfile.readline()

def connect():
    c = MyClient(9989)
    # On the second iteration, do_stuff() tries to send data and
    # hangs indefinitely.
    print c.do_stuff()

if __name__ == '__main__':
    for _ in xrange(3):
        try:
            connect()
        except MyException, e:
            print 'Caught:', e
            # This would be the workaround if I had access to the
            # MyClient object:
            #c.sock.close()
            #c.sockfile.close()

编辑:以下是(丑陋的)服务器代码:

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
s.bind(('localhost', 9989))
s.listen(5)
(c,a) = s.accept()
f = c.makefile()
print f.readline()
f.write('error\n')
f.flush()
(c2,a) = s.accept()
f = c.makefile()
print f.readline()
s.close()

4 回复 | 直到 7 年前

Mark Rushakoff 15 年前

这是垃圾收集的产物。即使对象是 ,不一定因此摧毁

您可能可以通过更改 connect 到

def connect():
    try:
        c = MyClient(9989)
        # On the second iteration, do_stuff() tries to send data and
        # hangs indefinitely.
        print c.do_stuff()
    finally:
        c.sock.close()
        c.sockfile.close()

或者,您可以定义 __enter__ 和 __exit__ 对于 MyClient ,然后呢 a with statement

def connect():
    with MyClient(9989) as c:
        print c.do_stuff()

这实际上与最后一次尝试相同。

u0b34a0f6ae 15 年前

我认为您应该提供一个MyClient.close()方法,并像这样编写connect():

def connect():
Â  Â  try:
Â  Â  Â  Â  c = MyClient(9989)
Â  Â  Â  Â  print c.do_stuff()
Â  Â  finally:
Â  Â  Â  Â  c.close()

这与类似文件的对象(以及with语句)完全相似

whatnick 15 年前

通过将相关对象设置为“无”,可以将垃圾收集器标记为清理。

bstpierre Edgar Aviles 15 年前

import socket

class MyException(Exception):
    pass

class MyClient(object):

    def __init__(self, port):
        self.sock = socket.create_connection(('localhost', port))
        self.sockfile = self.sock.makefile()

    def close(self):
        self.sock.close()
        self.sockfile.close()

    def do_stuff(self):
        self._send("do_stuff\n")
        response = self._receive()
        if response != "ok\n":
            raise MyException()
        return response

    def _send(self, cmd):
        self.sockfile.write(cmd)
        self.sockfile.flush()

    def _receive(self):
        return self.sockfile.readline()

def connect():
    try:
        c = MyClient(9989)
        print c.do_stuff()
    except MyException:
        print 'Caught MyException'
    finally:
        c.close()

if __name__ == '__main__':
    for _ in xrange(2):
        connect()