Calling methods in super class constructor or subclass constructor?

Question

1. Passing configuration to the __init__ method which calls register implicitely:

class Base:

    def __init__(self, *verbs):
        if not verbs:
          verbs = "get", "post"
        self._register(verbs)

    def _register(self, *verbs):
        pass


class Sub(Base):

    def __init__(self):
        super().__init__("get", "post", "put")

2. Calling register explicitely in the subclass' __init__ method:

class Base:

    def __init__(self):
        self._register("get", "post")

    def _register(self, *verbs):
        pass


class Sub(Base):

    def __init__(self):
        self._register("get", "post", "put")

I use Python 3.

What is better or more pythonic? Or is it only a matter of taste?

Answer 1

If everything extending the base class will behave like this, I would personally call from the base class's constructor. If not, and the behaviour varies, I would call from the sub class...

As for what is more Pythonic - don't subscribe to a cult - write code that works...

Martin

Answer 2

IMHO, the second way is better. The 'more pythonic' way is to make things as explicit as practical. You won't have to go track down the parent class constructor to see what it's doing with those arguments...

Answer 3

I think none of these options is good. The closest solution would probably be:

class Base(object):

    def __init__(self):
        self._register("get", "post")


class Sub(Base):

    def __init__(self):
        super(Sub, self).__init__()
        self._register("put")

I'm also wondering if it wouldn't be better to register the verbs at the class level. They are probably identical for all instances, so why are they registered for each instance individually?

Answer 4

I would definitely use the first form. The question I would ask myself is: "What if the initialization for the base class is modified, one day? do I want subclasses to benefit from the update or not?". In almost all of my code, the answer is a resounding yes… :)