twisted的DelayedCall

>>> l=[,,,,]
>>> del l[:]#只是删除列表的部分元素，列表仍然存在
>>> l
[, ]

#reactor循环执行的函数
def runUntilCurrent(self):
        """
        Run all pending timed calls.
        """
        if self.threadCallQueue:#执行线程化队列，在主线程中执行。
            # Keep track of how many calls we actually make, as we're
            # making them, in case another call is added to the queue
            # while we're in this loop.
            count = 0
            total = len(self.threadCallQueue)
            for (f, a, kw) in self.threadCallQueue:
                try:
                    f(*a, **kw)
                except:
                    log.err()
                count += 1
                if count == total:
                    break
            del self.threadCallQueue[:count]
            if self.threadCallQueue:#其他函数可以插入线程化函数
                self.wakeUp()

        # insert new delayed calls now
        self._insertNewDelayedCalls()#插入新的延时执行对象

        now = self.seconds()#读取系统时间 1970
        while self._pendingTimedCalls and (self._pendingTimedCalls[0].time <= now):定时时间到
            call = heappop(self._pendingTimedCalls)
            if call.cancelled:
                self._cancellations-=1
                continue

            if call.delayed_time > 0:
                call.activate_delay()#累加延时时间
                heappush(self._pendingTimedCalls, call)
                continue

            try:
                call.called = 1
                call.func(*call.args, **call.kw)#调用延时对象的函数
            except:
                log.deferr()
                if hasattr(call, "creator"):
                    e = "\n"
                    e += " C: previous exception occurred in " + \
                         "a DelayedCall created here:\n"
                    e += " C:"
                    e += "".join(call.creator).rstrip().replace("\n","\n C:")
                    e += "\n"
                    log.msg(e)

        if (self._cancellations > 50 and
             self._cancellations > len(self._pendingTimedCalls) >> 1):
            self._cancellations = 0
            self._pendingTimedCalls = [x for x in self._pendingTimedCalls
                                       if not x.cancelled]
            heapify(self._pendingTimedCalls)

        if self._justStopped:
            self._justStopped = False
            self.fireSystemEvent("shutdown")