Why do I need to call 'self' in this case?

Question

I am new to OOP and I am wondering why I need to supply the parameter MainWindow to the final line. If I call outside_func by itself, I don't need a parameter, but when I call it within a class i need to supply the class name for it to work. For example, MainWindow.class_func2() throws an error

class MainWindow():
    def __init__(self):
        print("in init")

    def claas_func(self):
        print ("func1")

    def class_func2(self):
        outside_func()

def outside_func():
    print('outside called')


instance = MainWindow()
MainWindow.class_func2(MainWindow)

Answer 1

You should take a look to @staticmethod

class MainWindow():
    def __init__(self):
        print("in init")

    def claas_func(self):
       print ("func1")

    @staticmethod
    def class_func2():
        return outside_func()

def outside_func():
    print('outside called')

instance = MainWindow()
>> in init

instance.class_func2()
>> outside called 

this @staticmethod (which itself it's something really cool called 'decorator') will make the method itself entirely callable without having pass 'self'.

Hope it helps

Answer 2

Try this instead. You have created an instance of MainWindow(). Now you can access its members with that.

class MainWindow():
    def __init__(self):
        print("in init")

    def claas_func(self):
        print ("func1")

    def class_func2(self):
        outside_func()

def outside_func():
    print('outside called')


instance = MainWindow()
instance.class_func2()

Also run this and notice it initializes the MainWindow() class 2x. I DO NOT recommend this second approach. It is redundant and not proper. But just so you can kind of see what it is doing.

class MainWindow():
    def __init__(self):
        print("in init")

    def claas_func(self):
        print ("func1")

    def class_func2(self):
        outside_func()

def outside_func():
    print('outside called')


instance = MainWindow()
MainWindow().class_func2()