Calling `super()` in parent class

Question

I'm reading Raymond Hettinger's Python’s super() considered super! About a page in, there's this example:

class Shape:
    def __init__(self, shapename, **kwds):
        self.shapename = shapename
        super().__init__(**kwds)        

class ColoredShape(Shape):
    def __init__(self, color, **kwds):
        self.color = color
        super().__init__(**kwds)

cs = ColoredShape(color='red', shapename='circle')

Why is it necessary to call super() in Shape here? My understanding is that this calls object.__init__(**kwds) since Shape implicitly inherits from object.

Even without that statement, we've already

• established shapename already in the parent's __init__,
• established the child class's color in an explicit method override,
• then invoked the parent's __init__ with super() in ColoredShape.

As far as I can tell, dropping this line produces the same behavior & functionality:

class Shape:  # (object)
    def __init__(self, shapename, **kwds):
        self.shapename = shapename
        # super().__init__(**kwds)

class ColoredShape(Shape):
    def __init__(self, color, **kwds):
        self.color = color
        super().__init__(**kwds)
    def check(self):
        print(self.color)
        print(self.shapename)

cs = ColoredShape(color='red', shapename='circle')

cs.check()
# red
# circle

What is the purpose of super() within Shape here?

Answer 1

I see that @user2357112 has already provided a correct answer. I was working on an example that I'd though I'd leave here because it's pretty much what user2357112 is describing. Consider a mixin class like this:

class PositionMixin:
    def __init__(self, x=0, y=0, **kwds):
        super().__init__(**kwds)
        self.x = x
        self.y = y

Let's say you apply that to your ColoredShape class:

class ColoredShape(Shape, PositionMixin):
    def __init__(self, color, **kwds):
        self.color = color
        super().__init__(**kwds)

If Shape doesn't call super.__init__, then when you do this:

myshape = ColoredShape('red', shapename='circle', x=1, y=1)
print(myshape.x, myshape.y)

You get:

Traceback (most recent call last):
  File "supertest.py", line 18, in <module>
    print (myshape.x, myshape.y)
AttributeError: 'ColoredShape' object has no attribute 'x'

The call to super.__init__ in shape is necessary to call the __init__ method on PositionMixin.