Steven Bethard wrote:
So when I'm writing a class and I define an __init__ method, I sometimes haven't called object.__init__, e.g.:
class C(object): def __init__(self, x): self.x = x
instead of
class C(object): def __init__(self, x): super(C, self).__init__() self.x = x
Looking at:
http://www.python.org/2.2.3/descrintro.html#__new__ "The built-in type 'object' has a dummy __new__ and a dummy __init__"
seems to suggest that the super call here is unnecessary. It's also not made in the Super class example from that document:
http://www.python.org/2.2.3/descrintro.html#superexample
I'm trying to get in the habit of calling super in all __init__ methods, but it seems like it's unnecessary when the only superclass is object.
Assuming that the base class of C doesn't get changed from object, are there consequences of not making this call?
Yes!
Consider what happens if you multi-subclass from the above C class and another class D.
class E(C, D):
def __init__(self, x):
super(E, self).__init__(x)
# some initialization for ENow E.__mro__ is (E,C,D,object). So:
1. E's __init__ should call C's __init__ (this happens due to super call in E.__init__)
2. C's __init__ should call D's __init__ (*this is why you need the super call in C.__init__*)
Without it, D.__init__ will not be called. Note that D.__init__ should not take any parameters in this case. Parameter similarity may be an issue in call-next-method technique.
However, if you know you will not mutli-subclass from C, you may leave out the super call.
HTH, Shalabh
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