dcrespo wrote:
>>Before, after, or during the .start() call, or somewhere else?
> I'd like to catch *just after* the .start() call.
Excellent. That makes it pretty easy then, since even though you are
spawning a thread to do the work, your main thread isn't expected to
continue processing in parallel. See my draft solution below. If it
doesn't seem to suit, explain where it fails you and we can try to
evolve it (assuming we're on the same page at all here).
> When you specify the case number 2, the IP must be valid for the
> computer where the program runs, otherwise, it raises an exception
> saying that "Can't assign requested address".
>
> MainProgram.py
> ...
> SrvrTCP = module.ThreadedTCPServer(ip,port)
> SrvrTCP.start()
> #Here, I want to know if the TCPServer started well.
Leave that part as it is. We'll override the start() method in your
subclass to solve your problem.
> module.py
> ...
> class ThreadedTCPServer(threading.Thread):
>
> def __init__(self, ip,port):
> threading.Thread.__init__(self)
> self.ip= ip
> self.port= port
self.startError = None
self.startedEvent = threading.Event()
def start(self):
'''start thread and wait for successful start'''
threading.Thread.start(self)
self.startedEvent.wait()
if self.startError:
raise self.startError
> def run(self):
> TCPServer((self.ip,self.port)) #Here, if the self.ip is
> invalid, it raises an exception.
> ...
We have to change the run() method slightly now:
def run(self):
try:
try:
TCPServer((self.ip, self.port))
except Exception, ex:
self.startError = ex
return
finally:
self.startedEvent.set()
# do the rest of the existing run() code here
Now that may not be perfect, since I'm not familiar with the TCPServer()
call. I've sort of assumed it does something quickly and returns, or
raises an exception if the input is bad. If it doesn't actually return
if it starts successfully, you would need a little different approach.
Probably adding a simple timeout to the self.startEvent.wait() call
would work.
Note also that you don't get the full original traceback with this
technique. I'm not sure you can, actually (though I can imagine that
with Python one could "stitch together" a traceback from a previous
exception as one raises a new exception). From what you describe,
however, it sounds like you just need to know that the exception
occurred, not the precise line of code down in TCPServer() where it was
originally raised.
I hope that helps and/or gives you some leads on a better solution.
-Peter
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