Take `self` without 'def __init__' an instance in Django - django

Question

'Generic view class' in Django puzzles me very much.
for instance:
class ProfileDetailView(DetailView):
def get_object(self):
username = self.kwargs.get('username')
if username is None:
raise Http404
return get_object_or_404(User, username__iexact=username, is_active=True)
Without the procedure of getting instantiated, it works as well.
What I can understand is:
class ProfileDetailView(DetailView):
def __init__(self, *args, **kwargs)
super().__init__(*args, **kwargs)
def get_object(self):
username = self.kwargs.get('username')
if username is None:
raise Http404
return get_object_or_404(User, username__iexact=username, is_active=True)
What's the mechanism behind it?

Answer 1

That's the fundamental principle of inheritance:
for your reference:
9. Classes — Python 3.6.3 documentation
class Mapping:
def __init__(self, iterable):
self.items_list = []
self.__update(iterable)
def update(self, iterable):
for item in iterable:
self.items_list.append(item)
__update = update # private copy of original update() method
class MappingSubclass(Mapping):
def update(self, keys, values):
# provides new signature for update()
# but does not break __init__()
for item in zip(keys, values):
self.items_list.append(item)

Answer 2

In Python3 super method behaves a bit more magically. It automatically figures out the parent of the class and implicitly passes the self as well. It has nothing to do specifically with Django itself. It's been done so to reduce the code redundancy. It is pretty irritating to be forced to change all super calls when changing the name of the class.
# Python2
class B(A):
def __init__(self, *args, **kwargs):
super(A, self).__init__(*args, **kwargs)
# Python 3
class B(A):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
Now as far as Django generic views are concerned, there is an as_view class method that creates a callable instance of the View, which delegates the call to dispatch method.

Answer 3

The __init__ method named constructor call automatically when you instantiated Class. Here As you inherit DetailView so super() call takes all __init__ functionality from DetailView.
class ProfileDetailView(DetailView): # here DetailView is inherited
def __init__(self, *args, **kwargs) # Own class(ProfileDetailView)'s __init__
super().__init__(*args, **kwargs) # it takes DetailView's __init__ behabiour
and it is not ProfileDetailView own so 2nd __init__ avoid self.