Duncan Booth wrote:
> bruno at modulix wrote:
>
>
>>Duncan Booth wrote:
>>(snip)
>>
>>>Usually though, if a subclass doesn't immediately call the base class
>>>constructors as the first thing it does in __init__ it indicates poor
>>>code and should be refactored.
>>
>>Not necessarily. It's a common case to have some computations to
>>do/some attributes to set in the derived class's __init__ before
>>calling the superclass's.
>>
>
>
> I did only say 'usually'. Can you actually think of any good examples where
> you have to set a derived attribute before you can call the base class
> constructor?
class Base(object):
def __init__(self, arg1):
self.attr1 = arg1
self.dothis()
def dothis(self):
return self.attr1
class Derived(Base):
def __init__(self, arg1, arg2=0):
self.attr2 = arg2
Base.__init__(self, arg1)
def dothis(self):
return self.attr1 + self.attr2
(snip)
> Perhaps if the base __init__ calls an overridden
> method, but at that point it sounds to me like something wants refactoring.
Why so ? This is a well-known pattern (template method). I don't see
what's wrong with it.
> I can think that you might have to do some computations to calculate
> parameters for the base __init__, but that is a separate issue.
--
bruno desthuilliers
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