[Tutor] Scope and elegance revisited

Kent Johnson kent37 at tds.net
Wed Jan 9 21:37:58 CET 2008

James Newton wrote:
> Hi Python Purists!
> I want all instances of a given class to share a piece of information,
> but I want to set that information on the fly.  I have found that this
> works:
>   class Foo(object):
>       # class_variable = None # There is no real need to declare this 
>       def __init__(self):
>           print self.__class__.class_variable

could be just self.class_variable, attributes are looked up in the class 
if not found in the instance (that's how method access works, e.g.).

>   def main():
>       Foo.class_variable = "Done"
>       Foo()
>   if __name__ == '__main__': main()
> Running the script prints out "Done" as expected.
> However, this looks ugly to me.  Is there a more elegant way of doing
> this?

Seems OK to me.

> To give you the context: my application allows you to select a skin for
> the user interface.  I want to set the access path to the skin folder as
> a class variable, so that all instances of that class use images from
> the appropriate folder.  The access path will be read in from a
> preferences file before any instances of the class are created.

Why do you have multiple instances of the class? You might be interested 
in the Borg pattern:


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