Local class variables? (mod_python problem)

[greg]

Rory Campbell-Lange wrote:

>     class Part (object):
>         totalgia = 0
>         def __init__(self, gia):
>             self.gia = gia  # gross internal area
>             self.giaratio = 0
>             Part.totalgia += self.gia
 >
>     if __name__ == '__main__':
>         p1 = Part(20)
>         p2 = Part(30)
>         for p in p1, p2:
>             p.addavgbm()
>             print p

You need another class, such as PartGroup, to keep track of
the totalgia of a group of parts (as an instance variable, not
a class variable). Then you can create a new instance of it
in your __main__ code, e.g.

   class PartGroup(object):

     def __init__(self):
       self.parts = []
       self.totalgia = 0

   class Part(object):

     def __init__(self, group, gia):
       self.gia = gia
       group.parts.append(self)
       group.gia += gia

   if __name__ == "__main__":
     parts = PartGroup()
     p1 = Part(parts, 10)
     p2 = Part(parts, 20)
     print parts.totalgia

A possible variation would be not to store the totalgia at
all, but have a function or method that calculates it from
the list of parts when you need it. Whether that's better or
not will depend on how frequently you need the value.

--
Greg



> 
> totalgia keeps incrementing when this code is used under mod_python.
> 
> We most certainly are in 'murky waters of accidental concurrent access'.
> A life vest would be gratefully received.
> 
> Kind regards
> Rory
> 
> 
> On 22/02/07, Rory Campbell-Lange (rory at campbell-lange.net) wrote:
> 
>>We have a set of classes using static methods to retain reference
>>variables between operations. The problem is that the static variables
>>are not reset between operations when used through mod_python.
>>
>>Although it is possible to reset the class variables between invocations
>>of the system, this has the potential of 'wiping out' these variables
>>when another user is using the system.
>>
>>Is there a way of getting the equivalent of 'local class variables'? In
>>other words, a way of making 'print a' and 'print b' below provide the
>>same output?
> 
> 
> On 22/02/07, Piet van Oostrum (piet at cs.uu.nl) wrote:
> 
>>>>>>>Rory Campbell-Lange <rory at campbell-lange.net> (RC) wrote:
> 
> 
>>There are several errors in your python code: quite a number of comma's
>>have to be replaced by semicolons (or newlines), and there is a spurious
>>comma.
> 
> 
> 
> On 22/02/07, Diez B. Roggisch (deets at nospam.web.de) wrote:
> 
>>Rory Campbell-Lange wrote:
> 
> 
>>It's very unclear what you mean here, and I'm additionally under the
>>impression that you are deep in the murky waters of accidential
>>concurrent access errors here. 
> 
> 
>