# ~*~ Twisted - A Python tale ~*~from time import sleep# Hello, I'm a developer and I mainly setup Wordpress.def install_wordpress(customer):  # Our hosting company Threads Ltd. is bad. I start installation and...  print "Start installation for", customer  # ...then wait till the installation finishes successfully. It is  # boring and I'm spending most of my time waiting while consuming  # resources (memory and some CPU cycles). It's because the process  # is *blocking*.  sleep(3)  print "All done for", customer# I do this all day long for our customersdef developer_day(customers):  for customer in customers:    install_wordpress(customer)developer_day(["Bill", "Elon", "Steve", "Mark"])

$ ./deferreds.py 1

------ Running example 1 ------Start installation for BillAll done for BillStart installation...* Elapsed time: 12.03 seconds

import threading# The company grew. We now have many customers and I can't handle the# workload. We are now 5 developers doing exactly the same thing.def developers_day(customers):  # But we now have to synchronize... a.k.a. bureaucracy  lock = threading.Lock()  #  def dev_day(id):    print "Goodmorning from developer", id    # Yuck - I hate locks...    lock.acquire()    while customers:      customer = customers.pop(0)      lock.release()      # My Python is less readable      install_wordpress(customer)      lock.acquire()    lock.release()    print "Bye from developer", id  # We go to work in the morning  devs = [threading.Thread(target=dev_day, args=(i,)) for i in range(5)]  [dev.start() for dev in devs]  # We leave for the evening  [dev.join() for dev in devs]# We now get more done in the same time but our dev process got more# complex. As we grew we spend more time managing queues than doing dev# work. We even had occasional deadlocks when processes got extremely# complex. The fact is that we are still mostly pressing buttons and# waiting but now we also spend some time in meetings.developers_day(["Customer %d" % i for i in xrange(15)])

$ ./deferreds.py 2

------ Running example 2 ------Goodmorning from developer 0Goodmorning from developer1Start installation forGoodmorning from developer 2Goodmorning from developer 3Customer 0...from developerCustomer 13 3Bye from developer 2* Elapsed time: 9.02 seconds

# For years we thought this was all there was... We kept hiring more# developers, more managers and buying servers. We were trying harder# optimising processes and fire-fighting while getting mediocre# performance in return. Till luckily one day our hosting# company decided to increase their fees and we decided to# switch to Twisted Ltd.!from twisted.internet import reactorfrom twisted.internet import deferfrom twisted.internet import task# Twisted has a slightly different approachdef schedule_install(customer):  # They are calling us back when a Wordpress installation completes.  # They connected the caller recognition system with our CRM and  # we know exactly what a call is about and what has to be done next.  #  # We now design processes of what has to happen on certain events.  def schedule_install_wordpress():      def on_done():        print "Callback: Finished installation for", customer    print "Scheduling: Installation for", customer    return task.deferLater(reactor, 3, on_done)  #  def all_done(_):    print "All done for", customer  #  # For each customer, we schedule these processes on the CRM  # and that  # is all our chief-Twisted developer has to do  d = schedule_install_wordpress()  d.addCallback(all_done)  #  return d# Yes, we don't need many developers anymore or any synchronization.# ~~ Super-powered Twisted developer ~~def twisted_developer_day(customers):  print "Goodmorning from Twisted developer"  #  # Here's what has to be done today  work = [schedule_install(customer) for customer in customers]  # Turn off the lights when done  join = defer.DeferredList(work)  join.addCallback(lambda _: reactor.stop())  #  print "Bye from Twisted developer!"# Even his day is particularly short!twisted_developer_day(["Customer %d" % i for i in xrange(15)])# Reactor, our secretary uses the CRM and follows-up on events!reactor.run()

------ Running example 3 ------Goodmorning from Twisted developerScheduling: Installation for Customer 0....Scheduling: Installation for Customer 14Bye from Twisted developer!Callback: Finished installation for Customer 0All done for Customer 0Callback: Finished installation for Customer 1All done for Customer 1...All done for Customer 14* Elapsed time: 3.18 seconds

# Twisted gave us utilities that make our code way more readable!@defer.inlineCallbacksdef inline_install(customer):  print "Scheduling: Installation for", customer  yield task.deferLater(reactor, 3, lambda: None)  print "Callback: Finished installation for", customer  print "All done for", customerdef twisted_developer_day(customers):  ... same as previously but using inline_install() instead of schedule_install()twisted_developer_day(["Customer %d" % i for i in xrange(15)])reactor.run()

@defer.inlineCallbacksdef inline_install(customer):  ... same as above# The new "problem" is that we have to manage all this concurrency to# avoid causing problems to others, but this is a nice problem to have.def twisted_developer_day(customers):  print "Goodmorning from Twisted developer"  work = (inline_install(customer) for customer in customers)  #  # We use the Cooperator mechanism to make the secretary not  # service more than 5 customers simultaneously.  coop = task.Cooperator()  join = defer.DeferredList([coop.coiterate(work) for i in xrange(5)])  #  join.addCallback(lambda _: reactor.stop())  print "Bye from Twisted developer!"twisted_developer_day(["Customer %d" % i for i in xrange(15)])reactor.run()# We are now more lean than ever, our customers happy, our hosting# bills ridiculously low and our performance stellar.# ~*~ THE END ~*~

$ ./deferreds.py 5------ Running example 5 ------Goodmorning from Twisted developerBye from Twisted developer!Scheduling: Installation for Customer 0...Callback: Finished installation for Customer 4All done for Customer 4Scheduling: Installation for Customer 5...Callback: Finished installation for Customer 14All done for Customer 14* Elapsed time: 9.19 seconds

..# 代碼片段  def dataReceived(self, data):    now = int(time.time())    for ftype, data in self.fpcodec.feed(data):      if ftype == 'oob':        self.msg('OOB:', repr(data))      elif ftype == 0x81: # 對服務器請求的心跳應答(這個是解析 防疲勞駕駛儀,發給gps上位機的,然后上位機發給服務器的)        self.msg('FP.PONG:', repr(data))      else:        self.msg('TODO:', (ftype, data))      d = deferToThread(self.redis.zadd, "beier:fpstat:fps", now, self.devid)      d.addCallback(self._doResult, extra)

# -*- coding: utf-8 -*-from twisted.internet import defer, reactorfrom twisted.internet.threads import deferToThreadimport functoolsimport time# 耗時操作 這是一個同步阻塞函數def mySleep(timeout):  time.sleep(timeout)  # 返回值相當于加進了callback里  return 3 def say(result):  print "耗時操作結束了, 并把它返回的結果給我了", result# 用functools.partial包裝一下, 傳遞參數進去cb = functools.partial(mySleep, 3)d = deferToThread(cb) d.addCallback(say)print "你還沒有結束我就執行了, 哈哈"reactor.run()