Twisted 任务调度派遣之 scheduling：定时执行程序

本文以简单易懂的语言来记录关于twisted定时执行某个任务的方法：

1. 如果要让某个程序在 x 秒之后执行，可以用 reactor.callLater() 方法：

# reactor.callLater() 在x秒之后启动f()函数
def f(s):
    print("this will run 2 seconds after it was scheduled: %s" % s)

reactor.callLater(2, f, "hello, world")
reactor.run()

2. 如果要接收程序的返回结果和处理异常，可以用 twisted.internet.task.deferLater(clock, delay, *args, callable=None, **kw)

def f(s):
    input("inputstr:")
    return "This will run 3.5 seconds after it was scheduled: %s" % s

# twisted.internet.task.deferLater(clock, delay, *args, callable=None, **kw)
d = task.deferLater(reactor, 2, f, "hello, world")  # 2秒之后触发f()

def call1(pos1):
    print(pos1)

d.addCallback(call1)   # 加入 call1() 处理函数，等f()延迟结束，会把f()返回的结果通过参数传给call1()
# 打印： This will run 3.5 seconds after it was scheduled: hello, world

def call2(pos1):
    print(pos1)
d.addCallback(call1)   # 加入 call2()处理函数，等 call1()延迟结束，会把 call1()返回的结果通过参数传给call2()，由于call1()没有返回值，所以这里是打印None

def errcalled(err):
    print(err)
d.addErrback(errcalled)  # 添加异常处理函数


reactor.run()

3. 如果要让一个循环每隔 x 秒重复一次，可以使用 twisted.internet.task.LoopingCall()

loopTimes = 3
failInTheEnd = False
_loopCounter = 0

def runEverySecond():   # Called at ever loop interval
    global _loopCounter

    if _loopCounter < loopTimes:
        _loopCounter += 1
        print('A new second has passed.')
        return

    if failInTheEnd:
        raise Exception('Failure during loop execution.')

    # We looped enough times.
    loop.stop()
    return


def cbLoopDone(result):     # Called when loop was stopped with success.
    print("Loop done.")
    reactor.stop()


def ebLoopFailed(failure):      # Called when loop execution failed.

    print(failure.getBriefTraceback())
    reactor.stop()


loop = task.LoopingCall(runEverySecond)

# Start looping every 1 second.
loopDeferred = loop.start(1.0)

# Add callbacks for stop and failure.
loopDeferred.addCallback(cbLoopDone)
loopDeferred.addErrback(ebLoopFailed)

reactor.run()

 

本文参考文章：

Scheduling tasks for the future