Le Thursday 31 July 2008 13:32:39 Thomas Troeger, vous avez écrit : > De : > Thomas Troeger <[EMAIL PROTECTED]> (Aioe.org NNTP Server) > À : > python-list@python.org > Date : > Aujourd'hui 13:32:39 > > > > Can someone explain to me the difference between a type and a class? > > If your confusion is of a more general nature I suggest reading the > introduction of `Design Patterns' (ISBN-10: 0201633612), under > `Specifying Object Interfaces'. > > In short: A type denotes a certain interface, i.e. a set of signatures, > whereas a class tells us how an object is implemented (like a > blueprint). A class can have many types if it implements all their > interfaces, and different classes can have the same type if they share a > common interface. The following example should clarify matters: >
Of course, this is what a type means in certain literature about OO (java-ish), but this absolutely not what type means in Python. Types are a family of object with a certain status, and they're type is "type", conventionnaly named a metatype in standard OO. There are three sort of objects in Python, in an inclusive order : - ordinary object, or instance, they could not be instantiated or subclassed (in general), and are all an instance of type "object" (or a subclass of it). - types, or classes, are all instance of type 'type' (or a subclass of it), they can be instantiated and they produce objects (ordinary object in general) with theirslef as a type. - metatypes or metaclass, are subclasses of "type", their instances are new types. For all tjis work together you must admit the following recursivity : 'type' is both a subclass and an instance of 'object' while 'object' is an instance of 'type'. -- _____________ Maric Michaud -- http://mail.python.org/mailman/listinfo/python-list
