Two attributes! Why?

[Steven D'Aprano]

On Fri, 28 Nov 2008 19:22:42 -0800, Emanuele D'Arrigo wrote:

> Hi everybody,
> 
> I'm having a naming/scoping/mangling issue. I have a class like this:
> 
> class MyClass(object):
>      __init__(self):
>          self.__myAttribute = None
> 
>      def myMethod(self, aValue):
>          attributeName = "__myAttribute"
>          setattr(self, attributeName, aValue)
> 
> It all looks good to me but when I use a debugger I find that
> 
> - myClass._MyClass__myAttribute = None
> 
> and
> 
> - myClass.__myAttribute = aValue
> 
> I can't quite understand why. 

This is a side-effect of name-mangling. Double-underscore names are only 
mangled when they are referred to directly as attributes, not when they 
are passed to setattr, getattr etc. Those functions don't do any name 
mangling.


-- 
Steven