What does Python's builtin __build_class__ do?

Question

In Python 3.1, there is a new builtin function I don\'t know in the builtins module:

__build_class__(...)
    __build_class__(func, name, *bases         


        

Answer 1

Compiling the PEP 3115 metaclass

Guido van Rossum said:

The PEP proposes that the class statement accepts keyword arguments, *args, and **kwds syntax as well as positional bases. This is a bit messy to compile and execute, but we already have this, of course, in the code for calling regular functions.

So I think it would be acceptable to this into a call to a new (hidden) built-in function, named __build_class__. Then that this class definition:

  class C(A, B, metaclass=M, other=42, *more_bases, *more_kwds):
    ...

would translate into this:

  C = __build_class__(<func>, 'C', A, B, metaclass=M, other=42,
*more_bases, *more_kwds)

where <func> is a function object for the class body.