python @abstractmethod decorator

Question

I have read python docs about abstract base classes:

From here:

abc.abstractmethod(function) A decorator indicating abstract method

Answer 1

Are you using python3 to run that code? If yes, you should know that declaring metaclass in python3 have changes you should do it like this instead:

import abc

class AbstractClass(metaclass=abc.ABCMeta):

  @abc.abstractmethod
  def abstractMethod(self):
      return

The full code and the explanation behind the answer is:

import abc

class AbstractClass(metaclass=abc.ABCMeta):

    @abc.abstractmethod
    def abstractMethod(self):
        return

class ConcreteClass(AbstractClass):

    def __init__(self):
        self.me = "me"

# Will get a TypeError without the following two lines:
#   def abstractMethod(self):
#       return 0

c = ConcreteClass()
c.abstractMethod()

If abstractMethod is not defined for ConcreteClass, the following exception will be raised when running the above code: TypeError: Can't instantiate abstract class ConcreteClass with abstract methods abstractMethod