does __new__ over ride __init__ in python

I have the following code:

class Demo:
    def __new__(self):
        self.__init__(self)
        print("Demo's __new__() invoked")
    def __init__(self):
        print("Demo's __init__() invoked")
                      
class Derived_Demo(Demo):
    def __new__(self):
        print("Derived_Demo's __new__() invoked")
    def __init__(self):
        print("Derived_Demo's __init__() invoked")

def main():
    obj1 = Derived_Demo()
    obj2 = Demo()

main()

I'm trying to understand the order of execution:

1. __new__ in the derived class is called first

2. why doesn't _init_ in the derived class called next?

Your code is fundamentally broken, which is why __init__ isn't being invoked as expected.

Per the docs for __new__:

If __new__() does not return an instance of cls, then the new instance’s __init__() method will not be invoked.

Your __new__ doesn't explicitly return anything, so it's returning None.

If you write it correctly (including removing explicit calls to __init__ within __new__, and explicitly delegating up the inheritance chain for Derived_Demo's __new__ and __init__), you code will work as expected:

class Demo:
    def __new__(cls):
        print("Demo's __new__() invoked")
        return super().__new__(cls)
    def __init__(self):
        print("Demo's __init__() invoked")

class Derived_Demo(Demo):
    def __new__(cls):
        print("Derived_Demo's __new__() invoked")
        return super().__new__(cls)
    def __init__(self):
        print("Derived_Demo's __init__() invoked")
        super().__init__()

def main():
    obj1 = Derived_Demo()
    obj2 = Demo()

main()

Try it online!

Which outputs:

Derived_Demo's __new__() invoked
Demo's __new__() invoked
Derived_Demo's __init__() invoked
Demo's __init__() invoked
Demo's __new__() invoked
Demo's __init__() invoked

where super() based dispatch completely runs all the __new__(s) then all the __init__(s) are run on the resulting object produced by __new__.