Using init and inheritance in python

Question

I'm a little confused regarding using __init__ and inheritance and would love to get some help with it.

I have a class [that can not be changed]:

class A(object):
    def __init__(self, param1 = 7, param2 = 10):
        self.x = param1
        self.y = param2     
    def func1(self):
        op1()
        op2()
    def func2(self):
        pass

this is some class that was written and I'm using it when overloading its functions:

class B(A):
    def func1(self)
        op3()
        op4()
    def func2(self)
        op5()

My problem starts here : I want to use Class B several times and sent each time different parameter:

---new .py file: ---
def myFunction():
    myInstance = B()

I want to do something like :

def myFunction():
    myInstance = B(40,"test")

I thought adding to B class - __init__ but the problem is that now I'm not sure what self it would use : explanation : Inside B class I have overloaded func2(self) I thought writing :

class B(A):
    def __init__(self, paramNumber, paramString)
        self.paramNumber = paramNumber
        self.paramString = paramString

but now in func2(self) , what self is used? the new one? the old one? will it work? meaning I will have : self.x , self.y and self.paramNumber self.parmString ?they are different "selfs"

Editing : Should I use super as well?

    class B(A):
    def __init__(self, paramNumber, paramString,param1, param2)
        self.paramNumber = paramNumber
        self.paramString = paramString
        super(B,self).__init__(param1,param2)

    def myFunction():
       myInstance = B(40,"test")
       // I will get : self.x = 7
       // self.y= 10
       // self.paramNumber=40
       //self.paramString = "test"

is this the correct solution?

They're the same self, but you've forgotten to call A.__init__ to set up .x and .y — Eric
– Eric, Commented Dec 23, 2013 at 9:40
Don't call A.__init__ directly as Eric mentions. Use super. — wim
– wim, Commented Dec 23, 2013 at 9:42
so wait - I need to add to my "def __init__(self,paramNumber, paramString) after setting this init, also the super?? — user1386966
– user1386966, Commented Dec 23, 2013 at 9:45
All methods of an object have the same self. It doesn't matter which class the methods come from; there aren't an A self and a B self you have to distinguish between. — user2357112
– user2357112, Commented Dec 23, 2013 at 9:51
why? If I'm using init is B class with self.xx and self.yy then how can I still reach self.x and self.y [ from A] — user1386966
– user1386966, Commented Dec 23, 2013 at 11:50

freakish · Accepted Answer · 2013-12-23 09:39:15Z

3

So basically you want to run __init__ from parent class inside child:

class B(A):
    def __init__(self, paramNumber, paramString):
        super(B, self).__init__(param1=1, param2=2)
        # the other code goes here

answered Dec 23, 2013 at 9:39

freakish

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2 Comments

user1386966 Over a year ago

I first use super and then add seld.paramString and self.paramNumber? I edited my question to what I hope is correct - is it ?

freakish Over a year ago

@user1386966 The order depends. Just look at the code and figure it out. Sometimes you want to fire super at the begining, sometimes at the end. I suppose that in your case it will be at the begining.

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