Question

我是新来的扭曲并试图建立一个程序，但我一直在做一个奇怪的行为

import sys
import json
import random
import time

from twisted.internet import threads, reactor
from twisted.python import log
from autobahn.twisted.websocket import WebSocketServerProtocol, WebSocketServerFactory


class DummyService():
    username = ''
    password = ''

    def __init__(self, username=username, password=password):
        print 'Connect to DummyService with user {} and password {}'.format(username, password)

    def slow_api_power(self, x):
        s = random.randint(1, 5)
        time.sleep(s)
        print "I am {} and my power is {}".format(x, x**2)

    def slow_go_to(self, x, lat, lng):
        s = random.randint(1, 5)
        time.sleep(s)
        print "I am {} and I am going to {} {}".format(x, lat, lng)


class DroneProtocol(WebSocketServerProtocol):

    # Persistent protocol state is kept in the factory.
    # Because a new instance of a protocol class is created for each connection,
    # protocols can't contain persistent state, that information must instead be stored in a protocol factory.

    def __init__(self, factory_protocol):
        self.factory = factory_protocol

    def onConnect(self, request):
        print("Client connecting: {0}".format(request.peer))

    def onOpen(self):
        print("WebSocket connection open.")

    def onMessage(self, payload, isBinary):
        if isBinary:
            print("Binary message received: {0} bytes".format(len(payload)))
        else:
            print("Text message received: {0}".format(payload.decode('utf8')))

        msg = json.loads(payload.decode('utf8'))

        if 'start' in msg['command']:
            for x in xrange(1, 4):
                self.factory.drones[x] = {
                    'name': x,
                    'instance': DummyService(username='user_' + str(x), password='password')
                }
                d = threads.deferToThread(self.factory.drones[x]['instance'].slow_api_power, x)
                d.addCallback(lambda ignore: self.factory.drones[x]['instance'].slow_go_to(x, lat=x+2, lng=x+4))


    def onClose(self, wasClean, code, reason):
        print("WebSocket connection closed: {0}".format(reason))


class DroneFactory(WebSocketServerFactory):

    drones = {}

    def buildProtocol(self, addr):
        return DroneProtocol(self)


if __name__ == '__main__':

    log.startLogging(sys.stdout)

    factory = DroneFactory()
    factory.protocol = DroneProtocol
    reactor.listenTCP(9999, DroneFactory())
    reactor.run()

我拥有的是：

2015-01-12 14:48:30-0300 [-] Log opened.
2015-01-12 14:48:30-0300 [-] DroneFactory starting on 9999
2015-01-12 14:48:30-0300 [-] Starting factory <__main__.DroneFactory instance at 0x102ed5dd0>
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] Client connecting: 127.0.0.1:60970
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] WebSocket connection open.
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] Text message received: {"command": "start"}
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] Connect to DummyService with user user_1 and password password
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] Connect to DummyService with user user_2 and password password
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] Connect to DummyService with user user_3 and password password
2015-01-12 14:48:35-0300 [DroneProtocol,0,127.0.0.1] WebSocket connection closed: connection was closed uncleanly (peer dropped the TCP connection without previous WebSocket closing handshake)
2015-01-12 14:48:38-0300 [DroneProtocol,0,127.0.0.1] I am 3 and my power is 9
2015-01-12 14:48:38-0300 [DroneProtocol,0,127.0.0.1]  I am 2 and my power is 4
2015-01-12 14:48:39-0300 [-] I am 3 and I am going to 5 7
2015-01-12 14:48:40-0300 [DroneProtocol,0,127.0.0.1] I am 1 and my power is 1
2015-01-12 14:48:42-0300 [-] I am 3 and I am going to 5 7
2015-01-12 14:48:44-0300 [-] I am 3 and I am going to 5 7

我无法理解为什么只执行最后一次回调。我有不同的延期，存储在字典中，为什么它们不分开？我的设计缺陷在哪里？

Answer 1

您误解了范围和嵌套函数的工作原理。考虑：

>>> def foo(x):
...     print x
... 
>>> L = []
>>> for i in range(3):
...     L.append(lambda: foo(i))
... 
>>> L[0]()
2
>>> L[1]()
2
>>> L[2]()
2
>>>

Answer 2

使用此代码解决

        if 'start' in msg['command']:
            for x in xrange(1, 4):
                self.factory.drones[x] = {
                    'name': x,
                    'instance': DummyService(username='user_' + str(x), password='password')
                }
                d = threads.deferToThread(self.factory.drones[x]['instance'].slow_api_power, x)
                d.addCallback(lambda ignore, p=x: self.factory.drones[p]['instance'].slow_go_to(p, lat=p+2, lng=p+4))

关键是要跟踪当前的x。另请参阅http://docs.python-guide.org/en/latest/writing/gotchas/#late-binding-closures

扭曲的deferToThread回调被覆盖

2 个答案: