how to display clock?, plus musings on the Nerd factor in Python

[John Benson]

Hi, here's some code I use to update a clock and some other stuff. You can
probably use the Tkinter mainloop() instead of the twisted reactor and
after(milliseconddelay, callback, args, ...) instead of the twisted
callLater routine if the twisted framework isn't being used.

You don't have to wrap the after()/callLater() stuff in a class like I did,
but it facilitates setup of various independent periodic events.

Attention veteran pythonistas: I'm a newcomer to python, so criticism of the
following code will be welcomed and assiduously studied:

...
from twisted.internet import reactor, tksupport
...

class Pulsar:
    def __init__(self, reactor, requiredparamslist=[], kwdparamsdict={},
                 pulseinterval=1.0, maxpulses=None,
callbeforefirstdelay=True):
        # begin create attributes
        self.reactor = reactor # from twisted.internet import reactor
        self.requiredparamslist = requiredparamslist
        self.kwdparamsdict = kwdparamsdict
        self.pulseinterval = float(pulseinterval)
        if maxpulses == None:
            self.maxpulses = None
        else:
            self.maxpulses = int(maxpulses)
        self.pulses = 0
        # end create attributes
        # start and/or schedule repetition
        if self.maxpulses == None or self.pulses < self.maxpulses:
            self.reactor.callLater(0, self.beforefirst)
            if (self.maxpulses == None) or (self.pulses < self.maxpulses):
                if callbeforefirstdelay:
                    self.IDelayedCall = self.reactor.callLater(0,
self.functionwrapper)
                else:
                    self.IDelayedCall =
self.reactor.callLater(self.pulseinterval, self.functionwrapper)
            else:
                # looks like there was just 1 repetition
                self.afterlast()
        else:
            # no repetitions!
            self.afterlast()
    def afterlast(self):
        pass
    def beforefirst(self):
        pass
    def cancel(self):
        self.IDelayedCall.cancel()
        self.maxpulses = self.pulses # paranoia, in case the cancel suffered
from a race condition
        self.cancelled()
    def cancelled(self):
        pass
    def functionwrapper(self):
        # assume that if we have been called/scheduled, we need to run the
function:
        self.pulses += 1
        apply(self.function, self.requiredparamslist, self.kwdparamsdict)
        if (self.maxpulses == None) or (self.pulses < self.maxpulses):
            self.IDelayedCall = self.reactor.callLater(self.pulseinterval,
self.functionwrapper)
        else:
            # that's all, folks: no more repetitions
            self.afterlast()
    def function(self):
        raise NotImplementedError # must be overridden


class Heartbeat(Pulsar):
    def afterlast(self):
        log("Heartbeat: that's all, folks!")
        reactor.stop()
    def beforefirst(self):
        log("XYZ Emulator entering service at %s" % time.asctime())
        ...
    def cancelled(self):
        log("Heartbeat: I was cancelled!", fei.ERROR)
        self.afterlast()
    def function(self):
        fei.timenow.set(time.asctime())
        log("Heartbeat %d " % self.pulses)

...
heartbeat = Heartbeat(reactor, pulseinterval=1)
reactor.listenTCP(5600, FalconFactory())
reactor.run()
...