observer pattern question #1 (reference to subject)

[Alan Isaac]

I have two questions about the "observer pattern" in Python.

This is question #1.  (I'll put the other is a separate post.)



Here is a standard example of the observer pattern in Python:



http://en.wikipedia.org/wiki/Observer_pattern



Contrast with this rather standard discussion:



http://www.dofactory.com/Patterns/PatternObserver.aspx#_self1



The difference I am focusing on is that in the latter,

the observer (investor) maintains a reference to the

subject (stock).  

(Many questions can be raised of course: see the discussion at

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/131499).



Is anything lost by not maintaining this reference (other 

than error checking ...)?  If I feel the observer needs 

access to the subject, what is wrong with just having the 

subject pass itself as part of the notification?



Thank you,

Alan Isaac