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# (a) the Software, and

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# Software and the Larger Work(s), and to sublicense the foregoing rights on

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import sys

# copied from: types.py#new_class

# Provide a PEP 3115 compliant mechanism for class creation

def new_class(name, bases=(), kwds=None, exec_body=None):

"""Create a class object dynamically using the appropriate metaclass."""

resolved_bases = resolve_bases(bases)

meta, ns, kwds = prepare_class(name, resolved_bases, kwds)

if exec_body is not None:

exec_body(ns)

if resolved_bases is not bases:

ns['__orig_bases__'] = bases

return meta(name, resolved_bases, ns, **kwds)

def resolve_bases(bases):

"""Resolve MRO entries dynamically as specified by PEP 560."""

new_bases = list(bases)

updated = False

shift = 0

for i, base in enumerate(bases):

if isinstance(base, type):

continue

if not hasattr(base, "__mro_entries__"):

continue

new_base = base.__mro_entries__(bases)

updated = True

if not isinstance(new_base, tuple):

raise TypeError("__mro_entries__ must return a tuple")

else:

new_bases[i+shift:i+shift+1] = new_base

shift += len(new_base) - 1

if not updated:

return bases

return tuple(new_bases)

def prepare_class(name, bases=(), kwds=None):

"""Call the __prepare__ method of the appropriate metaclass.

Returns (metaclass, namespace, kwds) as a 3-tuple

*metaclass* is the appropriate metaclass

*namespace* is the prepared class namespace

*kwds* is an updated copy of the passed in kwds argument with any

'metaclass' entry removed. If no kwds argument is passed in, this will

be an empty dict.

"""

if kwds is None:

kwds = {}

else:

kwds = dict(kwds) # Don't alter the provided mapping

if 'metaclass' in kwds:

meta = kwds.pop('metaclass')

else:

if bases:

meta = type(bases[0])

else:

meta = type

if isinstance(meta, type):

# when meta is a type, we first determine the most-derived metaclass

# instead of invoking the initial candidate directly

meta = _calculate_meta(meta, bases)

if hasattr(meta, '__prepare__'):

ns = meta.__prepare__(name, bases, **kwds)

else:

ns = {}

return meta, ns, kwds

def _calculate_meta(meta, bases):

"""Calculate the most derived metaclass."""

winner = meta

for base in bases:

base_meta = type(base)

if issubclass(winner, base_meta):

continue

if issubclass(base_meta, winner):

winner = base_meta

continue

# else:

raise TypeError("metaclass conflict: "

"the metaclass of a derived class "

"must be a (non-strict) subclass "

"of the metaclasses of all its bases")

return winner

# This will re-define the __build_class__ defined in functions.py

def __build_class__(func, name, *bases, **kwargs):

"""

__build_class__(func, name, *bases, metaclass=None, **kwds) -> class

Internal helper function used by the class statement.");

see: https://github.com/python/cpython/blob/36c1d1f1e52ba54007cbecb42c5599e5ff62aa52/Python/bltinmodule.c#L51

"""

if not hasattr(func, "__call__"):

raise TypeError("__build_class__: func must be a function")

if not isinstance(name, str):

raise TypeError("__build_class__: name is not a string, got '%s'" % type(name))

return new_class(name, bases=bases, kwds=kwargs, exec_body=func)

sys.modules['builtins'].__build_class__ = __build_class__