I'm looking for a little wisdom -- specifically, about thread locks and

I'm developing a Python-based product. One of the classes needs to hand out
unique IDs to clients as they connect for the first time. I generate these
by keeping an index integer in the instance that starts at zero,
incrementing it by one for every new client, and using the new value for the
unique ID. In order to prevent race conditions when two clients connect
almost simultaneously, I have another instance variable in my class that
holds a threading.lock(). I call acquire() on that lock just before the
increment-and-report code, and release() just after. So far so good.

That seemed to work just fine yesterday when I coded it. Then I shut down
Zope overnight and started it up again today. Now, I cannot create a new
instance of the class without getting the Zope error "UnpickleableError:
Cannot pickle <type 'thread.lock'> objects". (I'd swear it was working
yesterday, though.)

I thought "Okay, no problem. I'll just make the lock variable volatile,
since I don't really care whether it persists when Zope shuts down." So I
renamed the lock to begin with '_v_'. That solves my "UnpickleableError"
problem nicely. Unfortunately, it introduces a different problem: the code
that calls acquire() on the lock now throws "AttributeError: 'NoneType'
object has no attribute 'acquire'". I'm sure I initialize that variable to a
threading.Lock() in the object's __init__ method. So now I'm worried that
Zope is doing all kinds of pickling-unpickling activity behind the scenes,
and anything I have that's volatile can disappear without warning.

Are there any thread-wise Zopistas out there who can steer me right?



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Dr. Ian Beatty                           [EMAIL PROTECTED]
Physics Education Research Group              voice: 413.545.9483
Department of Physics                           fax: 413.545.4884
Univ. of Massachusetts              AIM: (available upon request)
Amherst, MA 01003-4525 USA
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