Alternative for inheritance in python

Question

How to save code duplication in the following scenario ?

say Aand B are two classes having a common function(say) name

class A(object):
    name = 'foo'

    @property
    def name(self):  # the common function
        return self.name

similarly B

class B(object):
    name = 'bar'

    @property
    def name(self):
        return self.name

One way would be to make a class from which both of them inherit from, and define name there.

Any good alternatives ?

Also see http://stackoverflow.com/questions/4139508. – FMc Jul 16 '13 at 03:18 — FMc, Jul 16 '13 at 03:18

score 1 · Answer 1 · answered Jul 16 '13 at 03:15

1

If you're really determined to avoid inheritance, just define a function outside of either class:

def get_name(object):
    return object.name

answered Jul 16 '13 at 03:15

Marius

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Vivek Jain · Answer 2 · 2013-07-16T03:14:39.227

0

class A(object):
    name = 'foo'

    def get_name(self):  # the common function
        return self.name

class B(A):
    pass

In this case B would inherit from A

edited Jul 16 '13 at 03:14

answered Jul 16 '13 at 03:09

Vivek Jain

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score 0 · Answer 3 · 2013-07-16T03:17:56.337

0

Is there a reason you can't have B inherit from A?

class B(A):
    name = 'bar'

edited Jul 16 '13 at 03:17

answered Jul 16 '13 at 03:09

Well, A isn't inheriting from B here. Just B from A, where is the issue with regular inheritance? – Jul 16 '13 at 03:17

score 0 · Answer 4 · answered Jul 16 '13 at 03:20

Since you are decorating name with @property, I am assuming you want this to be an instance variable. If you want this to return a more private variable, let's call it _name, you have to do:

class A(object):
    def __init__(self):
        self._name = 'foo'

    @property
    def name(self):
        return self._name

You can't have both a variable and a function have the same name, since the latter will simply override the former. If you want a base class that takes care of this, it would look like this:

class HasName(object):
    def __init__(self, name):
        self._name = name

    @property
    def name(self):
        return self._name

class A(HasName):
     def __init__(self):
         self._name = 'foo'

class B(HasName):
     def __init__(self):
         self._name = 'bar'

You can also call the constructor in HasName.

score 0 · Answer 5 · answered Jul 16 '13 at 03:26

Assuming self.name stands in for a more complex method, the easiest way to cut down on duplicated code is to move the function out to the module and have it take an arbitrary object as a parameter. Then, if you still want to tie the method directly to the class, you can add a short method that dispatches to the module function.

def _name(obj):
    return obj.name

class A(object):
     # ...

     @property
     def name(self):
         return _name(self)

class B(object):
     # ...

     @property
     def name(self):
         return _name(self)

Note that this will not work well if A.name and B.name have completely different behaviors. If the _name function starts checking the type of the object given, reconsider whether you really want to abstract that functionality in the first place.

Alternative for inheritance in python

5 Answers5