If you need something from super's __init__ to be done in addition to what is being done in the current class's __init__, you must call it yourself, since that will not happen automatically. But if you don't need anything from super's __init__, no need to call it. Example:
>>> class C(object):
def __init__(self):
self.b = 1
>>> class D(C):
def __init__(self):
super().__init__() # in Python 2 use super(D, self).__init__()
self.a = 1
>>> class E(C):
def __init__(self):
self.a = 1
>>> d = D()
>>> d.a
1
>>> d.b # This works because of the call to super's init
1
>>> e = E()
>>> e.a
1
>>> e.b # This is going to fail since nothing in E initializes b...
Traceback (most recent call last):
File "<pyshell#70>", line 1, in <module>
e.b # This is going to fail since nothing in E initializes b...
AttributeError: 'E' object has no attribute 'b'
__del__ is the same way, (but be wary of relying on __del__ for finalization - consider doing it via the with statement instead).
I rarely use __new__. I do all the initialization in __init__.