How do I initialize the base (super) class?

As of python 3.5.2, you can use:

class C(B):
def method(self, arg):
    super().method(arg)    # This does the same thing as:
                           # super(C, self).method(arg)

https://docs.python.org/3/library/functions.html#super

Python (until version 3) supports "old-style" and new-style classes. New-style classes are derived from object and are what you are using, and invoke their base class through super(), e.g.

class X(object):
  def __init__(self, x):
    pass

  def doit(self, bar):
    pass

class Y(X):
  def __init__(self):
    super(Y, self).__init__(123)

  def doit(self, foo):
    return super(Y, self).doit(foo)

Because python knows about old- and new-style classes, there are different ways to invoke a base method, which is why you've found multiple ways of doing so.

For completeness sake, old-style classes call base methods explicitly using the base class, i.e.

def doit(self, foo):
  return X.doit(self, foo)

But since you shouldn't be using old-style anymore, I wouldn't care about this too much.

Python 3 only knows about new-style classes (no matter if you derive from object or not).