Colin J. Williams wrote: >>>>I recently heard about 'new-style classes'. I am very sorry if this >>>>sounds like a newbie question, but what are they? I checked the Python >>>>Manual but did not find anything conclusive. Could someone please >>>>enlighten me? Thanks! >>> >>>"New style" classes are becoming the standard in Python, and must >>>always be declared as a subclass of a new style class, including built-in >>>classes. >> >> >> [Warning, advanced stuff ahead!] >> >> That's not entirely true. New-style classes need not be derived from a new- >> style class, they need to use the metaclass "type" or a derived. >> >> So you can also declare a new-style class as >> >> class new_class: >> __metaclass__ = type >> >> Or, if you want to switch a whole module with many classes to new-style, >> just set a >> >> __metaclass__ = type >> >> globally. >> > What are the pros and cons of the alternate approach?
The customary way is to use "class new_class(object):". There's no advantage in using __metaclass__ except that you can set it globally for all classes in that module (which can be confusing on its own). My comment mostly referred to "new-style classes must be declared as a subclass of a new-style class", which is not true. Reinhold -- http://mail.python.org/mailman/listinfo/python-list
