On Fri, 21 Dec 2007 09:26:36 -0800 (PST), Mangabasi <[EMAIL PROTECTED]> wrote: >Howdy, > >I think it is easier to explain my question with a short example: > >class Body: > def __init__(self, pos): > self.__dict__['pos'] = pos > > def __setattr__(self, name, value): > if name == 'pos': > print 'pos changed to', value > > self.__dict__[name] = value > >>>> b = Body([0, 0]) >>>> b.pos = [3, 4] >>>> pos changed to [3, 4] >>>> b.pos[0] = 5 # How do I detect this in the Body? >>>> > > >I would like to print 'pos changed to [5, 4]' when pos is modified >with direct access to the pos object (i.e. b.pos[0] = 5) > > >My first instinct is to modify the Body's __dict__ by using >metaclasses. >I don't have any experience with meta classes but from what I remember >this should be possible but I thought there could be a simpler way to >do this. > >What is the Pythonic way to do this? Can anybody provide a short >example for either case (with or without metaclasses).
You don't need metaclasses. You do need a wrapper around the list so that you can intercept calls to __setitem__ (and whatever else) which are made onto it. You might also consider making Body new-style (subclass object) and using a property instead of a __setattr__ implementation. You still need a wrapper, but the implementation of the rest of the feature should be simpler. Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
