Question

I am new to Python so please don’t flame me if I ask something too noobish 🙂

1.

Consider I have a class:

class Test:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def wow():
        print 5 * 5

Now I try to create an object of the class:

x = Test(3, 4)

This works as expected. However, when I try to call the method wow(), it returns an error, which is fixed by changing wow() to:

def wow(self)

Why do I need to include self and if I don’t, what does the method mean?

2. In the definition of __init__:

def __init__(self, x, y):
   self.x = x
   self.y = y

Why do I need to declare x and y, when I can do this:

def __init__(self):
    self.x = x
    self.y = y

I hope I am being clear…

Thanks for your time.

Answer 1

The instance reference in Python is explicit. That way it can be manipulated by e.g. decorators before finally being passed to the method.

We need to declare x and y as arguments to the function so that we can use their names within the function, bound to the arguments passed in the corresponding function call.