Python __new__ and __init__ with meta-classes

Reproducer.py

class AbstractClassError(Exception):
	pass

class M(type):
	# staticmethod
	def __new__(cls,	className, baseClasses,	members, abstract):
		newClass = type.__new__(cls, className, baseClasses, members)
		
		if abstract:
			def newnew(cls, *_, **__):
				raise AbstractClassError(f"Class is abstract")
			
			# keep original __new__ and exchange it with a dummy method throwing an error
			newClass.__new_orig__ = newClass.__new__
			newClass.__new__ = newnew
		else:
			# 1. replacing __new__ with original (preserved) method doesn't work
			newClass.__new__ = newClass.__new_orig__
			
			# 2. using a wrapper
			# def wrapper(cls, *args, **kwargs):
				# print("wrapper: ", cls, *args, kwargs)
				# return newClass.__new_orig__(cls, *args, **kwargs)
			
			# newClass.__new__ = wrapper
	
		return newClass
	
	# def __call__(cls, *args, **kwargs):
		# inst = cls.__new__(cls, *args, **kwargs)
		# inst.__init__(*args, **kwargs)
		# return inst
	
		# print(*args, kwargs)
		# return super().__call__(*args, **kwargs)


class A(metaclass=M, abstract=True):
	pass


class B(A, abstract=False):
	def __init__(self, arg):
		self.arg = arg

print("object.__new__  ", object.__new__)
print("A.__new_orig__  ", A.__new_orig__)
print("A.__new__       ", A.__new__)
print("B.__new__       ", B.__new__)

b = B.__new__(B, 5)
print("B.__new__(B, 5) ", b)
b.__init__(5)
print("b.__init__(5)   ", b.arg)


class X:
	pass


class Y(X):
	def __init__(self, arg):
		self.arg = arg


print("X.__new__       ", X.__new__)
print("Y.__new__       ", Y.__new__)


y = Y.__new__(Y, 3)
print("Y.__new__(Y, 3) ", y)
y.__init__(3)
print("y.__init__(3)   ", y.arg)

# o = object.__new__(object, 1)
# print(o)

y = Y(3)
print("y.arg           ", y.arg)

print("B.__new__       ", B.__new__)
b = B(5)
print("b.arg           ", y.arg)