CODEWITHSUNDEEP
pythoninheritanceattributes
Alex Winchell
Alex Winchell

Reputation: 51

Class Inheritance in Python

I'm new to python and trying to get a list of the classes an object's class inherits from. I'm trying to do this using the bases attribute but I'm not having any success. Can someone please help me out? 

def foo(C):
     print(list(C.__bases__))

class Thing(object):
    def f(self):
        print("Yo")

class Shape(Thing):
    def l(self):
        print("ain't no thang")

class Circle(Shape):
    def n(self):
        print("ain't no shape")

test = Circle()
foo(test)

Upvotes: 5

Views: 974

Answers (4)

Srikar Appalaraju
Srikar Appalaraju

Reputation: 73588

Use inspect, from documentation

Return a tuple of class cls’s base classes, including cls, in method resolution order. No class appears more than once in this tuple. Note that the method resolution order depends on cls’s type. Unless a very peculiar user-defined metatype is in use, cls will be the first element of the tuple.

>>> import inspect
>>> inspect.getmro(test.__class__)
(<class '__main__.Circle'>, <class '__main__.Shape'>, <class '__main__.Thing'>, <type 'object'>)
>>>

This traverses up the inheritance hierarchy & prints all classes, including object. Pretty Cool eh ?

Upvotes: 4

vinnydiehl
vinnydiehl

Reputation: 1704

print '\n'.join(base.__name__ for base in test.__class__.__bases__)

Or, using the inspect module:

from inspect import getmro
print '\n'.join(base.__name__ for base in getmro(test))

Upvotes: 2

Brian Cain
Brian Cain

Reputation: 14619

Your implementation of foo works. But you need to pass a class to foo, not an instance.

In [1]: def foo(C):
   ...:          print(list(C.__bases__))
   ...:

In [2]: class Thing(object):
   ...:         def f(self):
   ...:                 print("Yo")
   ...:

In [3]: class Shape(Thing):
   ...:         def l(self):
   ...:                 print("ain't no thang")
   ...:

In [4]: class Circle(Shape):
   ...:         def n(self):
   ...:                 print("ain't no shape")
   ...:

In [5]: test = Circle()

In [6]: foo(test)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-6-7b85deb1beaa> in <module>()
----> 1 foo(test)

<ipython-input-1-acd1789d43a9> in foo(C)
      1 def foo(C):
----> 2          print(list(C.__bases__))
      3

AttributeError: 'Circle' object has no attribute '__bases__'

In [7]: foo(Thing)
[<type 'object'>]

In [8]: foo(Circle)
[<class '__main__.Shape'>]

In [9]: foo(Shape)
[<class '__main__.Thing'>]

Upvotes: 1

nneonneo
nneonneo

Reputation: 179382

Only classes have __bases__; class instances do not. You can get the class object through an instance's __class__: use foo(test.__class__) or foo(Circle).

Upvotes: 6

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