Re: consequences of not calling object.__init__?

[Steve Holden]

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?

The principal one that I can see is that you are relying on this 
implementation feature to maintain forward compatibility, since I'm not 
aware of any pronouncement that says "object will *always* have a dummy 
__init__".

There's also the possibility that you might want to use a different base 
class later (for example, setting

    object = mySuperDebugObject
for debugging purposes). If that object has an __init__() method you'll 
have to put the calls in then anyway.

Perhaps a relevant question is how long it takes to call the __init__ 
method using super.

[EMAIL PROTECTED] ~/Projects/PyCON2005
$ python /usr/lib/python2.4/timeit.py -s "
class C(object):
  def __init__(self, x):
    self.x = x"  "C(1)"
100000 loops, best of 3: 2.69 usec per loop
[EMAIL PROTECTED] ~/Projects/PyCON2005
$ python /usr/lib/python2.4/timeit.py -s "
class C(object):
  def __init__(self, x):
    super(C, self).__init__()
    self.x = x"  "C(1)"
100000 loops, best of 3: 5.58 usec per loop
So, even on my cronky old 1.3 GHz laptop [1] you only lose 3 
microseconds per object creation. You'll have to decide how significant 
that is.

regards
 Steve
[1]: Freaky - I had just typed this when the doorbell went, and it was 
the UPS driver delivering the new laptop!
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