> > I used to have the following code to collect all (old style) class > > names defined in the current module to a list called reg: > > > > > > def meta( reg ): > > def _meta( name, bases, dictionary ): > > reg.append( name ) > > return _meta > > > > reg = [ ] > > __metaclass__ = meta( reg ) > > > > class c1: > > pass > > > > class c2: > > pass > > > > print reg > > That code does not create classes. Here's a slightly simplified version: > > >> reg = [] > >>> def __metaclass__(name, bases, dict): > ... reg.append(name) > ... > >>> class A: pass > ... > >>> reg > ['A'] > >>> A is None > True # oops! > > > This would correctly print [ 'c1', 'c2' ]. Now I would like to switch > > to new style classes but replacing class c1: and class c2: by class > > c1(object): and class c2(object): doesn't work because the metaclass > > associated with object will be called and not mine. Of course if I > > would add __metaclass__ = meta(reg) to all class definitions that > > would work, but how do I do this on the module level? > > If present, __metaclass__ serves as a factory for classes without an > explicit base class. For example, > > __metaclass__ = type > > would turn c1 and c2 into newstyle classes (that inherit from object). > If you want side effects you can wrap the metaclass into a function: > > >>> reg = [] > >>> def __metaclass__(name, bases, dict): > ... reg.append(name) > ... return type(name, bases, dict) > ... > >>> class A: pass > ... > >>> class B: pass > ... > >>> reg > ['A', 'B'] > >>> issubclass(A, object) > True
Thanks a lot, and sorry for the copy-paste error, I had the 'return type(...)' line but didn't know that this already creates new-style classes. -- http://mail.python.org/mailman/listinfo/python-list
