强制子类写入docstring

使用 __init_subclass__ . 这个 __doc__ 类的属性设置为类的docstring的值;如果没有docstring,则属性设置为 None

class Study(ABC):

   """ Define the purpose of the study here """

   def __init__(self, value):
      self.value = value

   @abstractmethod
   def do_something(self):
      pass

   def __init_subclass__(cls):
      if cls.__doc__ is None:
          raise AttributeError("No docstring")

那么

>>> class GoodStudy(Study):
...   "Do some stuff"
...
>>> class BadStudy(Study):
...   pass
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<path>/abc.py", line 126, in __new__
    cls = super().__new__(mcls, name, bases, namespace, **kwargs)
  File "tmp.py", line 16, in __init_subclass__
    raise AttributeError("No docstring")
AttributeError: No docstring