"Carl J. Van Arsdall" <[EMAIL PROTECTED]> wrote:
> class Shared:
> def __init__(self):
> self.__userData= {}
> self.__mutex = threading.Lock() #lock object
>
> def getVar(self, variableName):
> temp = None
> error = 0
> self.__mutex.acquire() #accessing shared dictionary
> try:
> try:
> temp = self.__userData[variableName]
> except:
> print "Variable doesn't exist in shared space"
> raise ValueError
> finally:
> self.__mutex.release()
> return temp
A few comments on this.
First, it's almost always a bad idea to have a bare "except:", because that
catches *every* possible exception. You want to catch as specific an
exception as you can (in this case, I suspect that's KeyError).
Second, I'm not sure if your intent was to return from the function or to
raise an exception on an unknown variableName. You can't do both! Quoting
from http://docs.python.org/ref/try.html..
> When an exception occurs in the try clause, the exception is temporarily
> saved, the finally clause is executed, and then the saved exception is
> re-raised. If the finally clause raises another exception or executes a
> return or break statement, the saved exception is lost.
so with the code you posted (from sight; I haven't tried running it), what
will happen is:
1) __userData[variableName] raises KeyError
2) The KeyError is caught by the inner try block and the except block runs,
which in turn raises ValueError
3) The ValueError is caught by the outer try block and the finally block
runs, releasing the mutex, discarding the ValueError exception, and
returning temp
4) Whoever called getVar() will see a normal return, with a return value of
None (because that's what temp was set to in the first line of getVar()
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