yes, with metaclasses (was Re: Read-only class definitions?)

[Troels Therkelsen]

In article <xxxp9.32771$Fz.941846 at news1.tin.it>, Alex Martelli wrote:
> In 2.2.* (and later), a class IS a class instance -- the class of
> the class is also known as its _metaclass_.  Inherit from the
> builtin type named 'type', override whatever you wish, and make
> your new metaclass the class's metaclass (by setting __metaclass__
> in class body, or inheriting from another class with that custom
> metaclass, etc).
> 
> Example:
> 
> class metaNoDel(type):
>     def __delattr__(self, name):
>         raise TypeError, "Can't delete attr %s from NoDel class!" % name
> 
> class NoDel:
>     __metaclass__ = metaNoDel
> 
> class a(NoDel):
>     def afunc(self):
>         pass
> 
> class b(a):
>     pass
> 
> c = b()
> c.afunc()
> del a.afunc
> c.afunc()
> 

Alex,

Thanks a lot for the pointer on the __metaclass__, I had totally ignored that
aspect.  This will be useful in another project I'm working on :-)

However, what would prevent the code from doing

del a.__metaclass__.__delattr__
del a.afunc

?


Regards,

Troels Therkelsen