method that can be called from a class and also from an instance
steve+comp.lang.python at pearwood.info
Fri Nov 23 05:32:31 CET 2012
On Thu, 22 Nov 2012 16:51:27 +0100, Peter Otten wrote:
> Marc Aymerich wrote:
>> I want to create a method within a class that is able to accept either
>> a class or an instance.
> Why would you overload a method that way?
The use-case I have is that I have a number of classes with default
state. Most instances don't override any of the state, so the instances
don't add anything except an extra conceptual layer:
instance = MyClass() # notice that there are no arguments passed
Since the instances don't have any state except for that already held by
the class, they are redundant and pointless. Just knowing the class is
enough to specify the behaviour. If I used class methods, I could do this:
But here's the thing -- sometimes I *do* have instances that override the
instance = MyClass(x, y, z)
Now if method is a class method, my per-instance state is ignored. So I
want a method that can be called from the class, and see the default
state, or from the instance, and see the per-instance state. Neither
classmethod, staticmethod nor ordinary instance methods do the job, but
my custom dualmethod does.
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