[Python] Python abstract class shall force derived classes to initialize variable in __init__

I want to have an abstract class which forces every derived class to set certain attributes in its __init__ method.

I've looked at several questions which did not fully solve my problem, specifically here or here. This looked promising but I couldn't manage to get it working.

I assume my desired outcome could look like the following pseudo code:

from abc import ABCMeta, abstractmethod


class Quadrature(object, metaclass=ABCMeta):

@someMagicKeyword #<==== This is what I want, but can't get working
xyz

@someMagicKeyword #<==== This is what I want, but can't get working
weights


@abstractmethod
def __init__(self, order):
pass


def someStupidFunctionDefinedHere(self, n):
return self.xyz+self.weights+n



class QuadratureWhichWorks(Quadrature):
# This shall work because we initialize xyz and weights in __init__
def __init__(self,order):
self.xyz = 123
self.weights = 456

class QuadratureWhichShallNotWork(Quadrature):
# Does not initialize self.weights
def __init__(self,order):
self.xyz = 123


Here are some of the things I have tried:

from abc import ABCMeta, abstractmethod


class Quadrature(object, metaclass=ABCMeta):

@property
@abstractmethod
def xyz(self):
pass


@property
@abstractmethod
def weights(self):
pass


@abstractmethod
def __init__(self, order):
pass


def someStupidFunctionDefinedHere(self, n):
return self.xyz+self.weights+n



class QuadratureWhichWorks(Quadrature):
# This shall work because we initialize xyz and weights in __init__
def __init__(self,order):
self.xyz = 123
self.weights = 456


Then I try to create an instance:

>>> from example1 import *
>>> Q = QuadratureWhichWorks(10)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class QuadratureWhichWorks with abstract methods weights, xyz
>>>


Which tells me to implement the methods, but I thought I said that these are properties?

My current work-around has the flaw, that the __init__ method can be overwritten in the derived classes but for now this at least ensures (to me) that I always know that the requested properties are set:

from abc import ABCMeta, abstractmethod


class Quadrature(object, metaclass=ABCMeta):

@abstractmethod
def computexyz(self,order):
pass


@abstractmethod
def computeweights(self,order):
pass


def __init__(self, order):
self.xyz = self.computexyz(order)
self.weights = self.computeweights(order)

def someStupidFunctionDefinedHere(self, n):
return self.xyz+self.weights+n



class QuadratureWhichWorks(Quadrature):

def computexyz(self,order):
return order*123

def computeweights(self,order):
return order*456


class HereComesTheProblem(Quadrature):

def __init__(self,order):
self.xyz = 123
# but nothing is done with weights

def computexyz(self,order):
return order*123

def computeweights(self,order): # will not be used
return order*456


But the problem is

>>> from example2 import *
>>> Q = HereComesTheProblem(10)
>>> Q.xyz
123
>>> Q.weights
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'HereComesTheProblem' object has no attribute 'weights'


How is this implemented correctly?

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