Not a bug, and not restricted to class methods. Same thing happens of you
define a list in your default parameter list and mutate it in your method
body. The issue is you have a reference to the same mutable object (the one
defined in te paramter list) when you're not passing an explicit value. If
you need a default value for a mutable object, always set it inside your
method body, not in the parameter list.
On Friday, August 10, 2012, Jay Goodman wrote:
> I found some 'wierdness' with classmethods today (in 2.5). I have a
> classmethod with kwargs, and I noticed that the kwarg was, somehow, taking
> on a global scope.
>
> example:
> ---------
> @classmethod
> def classMethodName (cls, argName, kwargName={}):
> doStuff
> --------
>
> 1st Call--> classMethodName(argName) # kwarg is not passed in
> kwarg is empty
> kwarg (dictionary) ends up getting filled with data
> kwarg is NOT cleared (clearing it is a workaround, though)
>
> 2nd Call--> classMethodName(argName) #same as the first
> kwarg is NOT EMPTY--it contains the data from the 1st call
>
> So somehow, the kwarg is getting global scope? Is this how classmethods
> are designed to work? At first I thought I screwed up and this variable
> was defined globally, but that is not the case. Also, this issue can be
> worked around by either clearing the dictionary or using kwargs. I was
> just looking for a better understanding as to why it was happening this
> way?
> Any takers?
> thanks!
>
>
>
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