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Find the closest relative


Hi I have three objects, all of them are instances of classes derived
from a base class. Now, given one of the instance, I want to find the
closest relative of the other two. How can I do this?

This is how I implemented; I guess there must be elegant way to do
this...

def find_closest_relative(a,b,c):
    c1 = b.__class__
    c2 = b.__class__

    while True:
        if isinstance(a, c1):
            return b
        if isinstance(a, c2):
            return c
        c1 = c1.__base__
        c2 = c1.__base__

-
Suresh

On May 25, 12:31 am, "jm.sur@no.spam.gmail.com"

I can't see how your code does what you describe.

> Now, given one of the instance, I want to find the
> closest relative of the other two.

What influence would an object have over the closest relative of two
other objects?  The closet relative of two other objects is
independent of any third object.  Do you want to find the closest
relative of 3 objects?  If so, this might work:

import inspect

class A(object): pass
class X(object): pass

class B(A, X): pass  #an object of this class has A as a base class
class C(A, X): pass
class D(A, X): pass

class E(C): pass  #an object of this class has A as a base class
class F(D): pass  #an object of this class has A as a base class

def closestRelative(x, y, z):
    b1 = inspect.getmro(x.__class__)
    b2 = inspect.getmro(y.__class__)
    b3 = inspect.getmro(z.__class__)

    for elmt in b1:
        if elmt in b2 and elmt in b3:
            return elmt
    return None

b = B()
e = E()
f = F()

print closestRelative(b, e, f)

However, you should probably post an example of a class structure and
describe what you want to happen when you have three instance of the
various classes.

On May 25, 12:40 pm, 7stud <bbxx789_0@yahoo.com> wrote:

    Vehicle
    |
    |--- Two Wheeler
    |       |
    |       |--- BatteryPowered
    |       |--- PetrolPowered
    |       |--- DieselPowered
    |
    |--- Three Wheeler
    |       |
    |       |--- AutoRicksaw
    |
    |--- Four Wheeler
    |       |
    |       |--- GeneralTrans
    |       |       |--- Car
    |       |               |--- Car1
    |       |               |--- Car2
    |       |               |--- Car3
    |       |
    |       |--- PublicTrans
    |       |       |--- Bus
    |       |               |--- Bus1
    |       |               |--- Bus2
    |       |--- Goods
    |               |--- Lorry
                            |--- Lorry1
                            |--- Lorry2
                            |--- Lorry3

 Now given one instance of some type, I want to choose between second
and third, whichever
 is closest relative to the first object.
 Eg.
    Instance(Car1), Instance(Lorry1), Instance(AutoRicksaw)  =>
Instance(Lorry1)

On May 25, 12:40 pm, 7stud <bbxx789_0@yahoo.com> wrote:

Sorry, It was nor phrased well. I want to find the closest relative of
the first object among the second and third.i.e. I want to choose
either second or third object based on how close they are on the class
hierarchy to the first object.

En Fri, 25 May 2007 05:09:00 -0300, jm.sur@no.spam.gmail.com  
<jm.sur@gmail.com> escribi:

If your classes actually form a tree (you have only single inheritance)  
then you may use the mro():

Car1.mro() = [Car, GeneralTrans, FourWheeler, Vehicle, object]
Lorry1.mro() = [Lorry, Goods, FourWheeler, Vehicle, object]
AutoRicksaw.mro() = [ThreeWeeler, Vehicle, object]

Now you have to find the first item in Lorr1.mro that appears also in  
Car1.mro, and the same for AutoRicksaw.mro; the least index on Car1.mro  
wins (Or the least index in the other list; or the least sum; that depends  
on your exact definition of "closest relative").
(Under the Argentinian law, you measure how "close" two relatives are,  
starting with one person, going up the tree until you find a common  
ancestor, and going down to the other person. That is, summing up the  
indices on both "mro" lists for the common ancestor).

--
Gabriel Genellina

On May 25, 12:08 pm, "Gabriel Genellina" <gagsl-@yahoo.com.ar>
wrote:

The distance between 2 classes is (roughly) the sum of the distances
to the root class minus twice the distance from their common ancestor
to the root class, or:

def Distance(class1, class2):
        set1, set2 = set(class1.mro()), set(class2.mro())
        return len(set1) + len(set2) - 2 * len(set1 & set2)

Seems to work OK.

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