Kent Johnson wrote: > Steven Bethard wrote: >> I don't run into this often, but when I do, I usually go Jack >> Diederich's route:: >> >> class A(object): >> class __metaclass__(type): >> def __init__(cls, name, bases, classdict): >> cls.sum = sum(xrange(10)) > > I think you should call the superclass __init__ as well: > > class __metaclass__(type): > def __init__(cls, name, bases, classdict): > super(__metaclass__, cls).__init__(name, bases, classdict) > cls.sum = sum(xrange(10))
Yes, thanks for the catch. I'd like to use super there, but I think you'll find that it doesn't work because of the order in which A and __metaclass__ get created: >>> class A(object): ... class __metaclass__(type): ... def __init__(cls, name, bases, cdict): ... super(__metaclass__, cls).__init__(name, bases, cdict) ... cls.sum = sum(xrange(10)) ... Traceback (most recent call last): File "<interactive input>", line 1, in ? File "<interactive input>", line 4, in __init__ NameError: global name '__metaclass__' is not defined >>> class A(object): ... class __metaclass__(type): ... def __init__(cls, name, bases, classdict): ... super(A.__metaclass__, cls).__init__(name, bases, classdict) ... cls.sum = sum(xrange(10)) ... Traceback (most recent call last): File "<interactive input>", line 1, in ? File "<interactive input>", line 4, in __init__ NameError: global name 'A' is not defined I played around with a few solutions to this problem, but it seems like the cleanest one is just to avoid super: >>> class A(object): ... class __metaclass__(type): ... def __init__(cls, name, bases, cldict): ... type.__init__(cls, name, bases, cldict) ... cls.sum = sum(xrange(10)) ... Of course, this means you can't use some sorts of multiple inheritance with A.__metaclass__... STeVe P.S. Here's the best way I found that still uses super: >>> class A(object): ... class __metaclass__(type): ... def __init__(cls, name, bases, cldict): ... try: ... meta = A.__metaclass__ ... except NameError: ... meta = cldict['__metaclass__'] ... super(meta, cls).__init__(name, bases, cldict) ... cls.sum = sum(xrange(10)) ... -- http://mail.python.org/mailman/listinfo/python-list
