Reason for self when extending objects (Python)

So say I am extending an object called Frame (found in 'tkinter'), as shown below,

class GraphRegion(Frame):

    def __init__(self, master):
        Frame.__init__(self,master)

Now, I know why 'master' is needed. Why does Frame.__init__ need 'self'? Doesn't 'self' point to GraphRegion? What is this actually telling the object 'Frame'? Is it to create GraphRegion as a type 'Frame'?

Solution

Although Martjin's answer is great, I'm going to expand on it, in some, let's say, "lower level" terms.

Basically, whenever you create a new GraphRegion object (myobject = GraphRegion(master)), __init__ is called with the new object as the first parameter (self), and the master argument as the second parameter.

Basically, if you do this:

myobject = GraphRegion(master)

__init__ get's called like this:

__init__(myobject, master)

This is because you often want to assign properties to specific instances of an object, and self lets you do that. For example, if I had a class Movie, where each instance of it had it's own title, I would use self like this:

class Movie(object):
    def __init__(self, title):
        self.title = title

That way, every instance of Movie can have it's own title.

Now, whenever you run Frame.__init__(self, master), that __init__ function often needs to modify the specific instance of the GraphRegion class you're creating (the object you're creating), and self is that instance, so you pass it to the __init__ method.