[Python-bugs-list] [ python-Bugs-599452 ] Method resolution order in Py 2.2 - 2.3

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Bugs item #599452, was opened at 2002-08-23 19:00
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=599452&group_id=5470

Category: Python Interpreter Core
Group: None
>Status: Closed
>Resolution: Invalid
Priority: 5
Submitted By: Alex A. Naanou (alex_nanou)
Assigned to: Nobody/Anonymous (nobody)
Summary: Method resolution order in Py 2.2 - 2.3

Initial Comment:
-- from "What's new in Python 2.2" 
      section 2.3 "Multiple Inheritance: The Diamond Rule"
"""
Multiple inheritance has also been made more useful 
through changing the rules under which names are 
resolved.
"""

Well, for a feature that was officially "introduced" in
version 2.2 it shows a remarkable lack of presence 
(even in the CVS versions of 2.3)!!
// though, I could have missed something (an elephant in
// my backyard!), if so please point it out...


Description:
Actually, there is nothing wrong... the function in 
question is just not changed since version 2.1.x, thus 
we get the old style lookup table (Method resolution 
order).
I'll try not to get too carried away.. here is an 
example 'almost' literally taken from that same section 
of the documentation mentioned above:

---cut---
class A:
    def save(self):
        return "I am 'A.save'"
class B(A):
    pass
class C(A):
    def save(self):
        return "I am 'C.save'"
class D(B,C):
    pass

print D().save()

---uncut---

Expected Results:
  something printed EXACTLY like:
>>> I am 'C.save'


Actual Result:
//here is the part where I faint...   :|
we get:
>>> I am 'A.save'


The results are identical for:
- Python 2.2
- Python 2.2.1
- Python 2.3 (CVS)


Thanks!!


----------------------------------------------------------------------

Comment By: Neil Schemenauer (nascheme)
Date: 2002-08-23 19:30

Message:
Logged In: YES 
user_id=35752

You need to make 'A' subclass from 'object' in order to get
the new
MRO behavior.

----------------------------------------------------------------------

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https://sourceforge.net/tracker/?func=detail&atid=105470&aid=599452&group_id=5470