Python Validation

validators.py

from abc import ABC, abstractmethod

class Validator(ABC):
    
    def __set_name__(self, owner, name):
        self.private_name = f'_{name}'
        
    def __get__(self, obj, objtype=None):
        return getattr(obj, self.private_name)
    
    def __set__(self, obj, value):
        self.validate(value)
        setattr(obj, self.private_name, value)
        
    @abstractmethod
    def validate(self, value):
        pass
    
class OneOf(Validator):
    
    def __init__(self, *options):
        self.options = set(options)
        
    def validate(self, value):
        if value not in self.options:
            raise ValueError(f'{value!r} is not a valid option. Should be one of {self.options!r}')
            
class Sample:
    
    group = OneOf('A', 'B')
    
    def __init__(self, group):
        self.group = group
        
Sample('A') # OK
Sample('C') # 'C' is not a valid option. Should be one of {'A', 'B'}