On May 28, 4:37 pm, Christian Heimes <li...@cheimes.de> wrote: > LittleGrasshopper wrote: > > This is probably trivial, but it's driving me mad somehow. All (new > > style) classes are instances of 'type' by default, unless a custom > > metaclass is specified. I take this to mean that when a class > > declaration is found in the code, an instance of 'type' representing > > that class is created by calling type.__init__. What really gets me is > > how can 'type' be an instance of itself. In order to create 'type' we > > would need to call type.__init__, but it seems at this point it > > wouldn't exist. Probably a dumb question, which I hope someone can > > explain in some detail. > > The classes 'type' and 'object' are written in C. You can do things in C > code that aren't possible from pure Python code. The circular > dependencies between 'type' and 'object' are created during the boot > strapping phase of the interpreter. > > >>> type(type) > <type 'type'> > >>> type.__bases__ > (<type 'object'>,) > >>> object.__bases__ > () > >>> type(object) > > <type 'type'> > > Christian
And just to clarify that I do really understand what this means, I gather that what it entails is that 'type' is an instance of itself just from a conceptual point of view. In other words, the code for the (meta)class 'type' is created statically by object code (compiled C code) before the python runtime is initiated (you referred to it as the interpreter bootstrapping phase.) I also guess that this code sets __class__ and __metaclass__ to the 'type' object itself (I am guessing a self-referencial pointer in C.) While I just am hypothesizing on the details, please let me know if you sense that I have misunderstood any essential part of your explanation. Thanks, Lukas -- http://mail.python.org/mailman/listinfo/python-list
