[Tutor] Little subclass understanding problem

[Tom]

I am trying to understand what happens in the following scenario:

class Sub_class(Base_class):
    def __init__(self, data):
        Base_class.__init__(self, data)

as in:

# snippet from http://viner.tv/go?set
class Set(list):
    def __init__(self, value = []):
        list.__init__([])


The last line is the one I don't understand. Nothing appears to be
assigned or instantiated.

I have just re-read the relevant part of Wesley Chun's 'Core' book,
again, and think I *may* understand.

Base_class.__init__(self, data)

is *kind of* like saying:

self.Base_class.__init__(data)

i.e. it's doing something *to* self. But then the 2nd example above
doesn't make sense! It looks like list.__init__([]) is doing something
special just because of where it is, i.e. in the class definition of a
subclass of list.

Help!

If anyone has a better way of explaining this / thinking about this, I
would be most grateful!