List all base classes in a hierarchy of given class?


Given a class Foo (whether it is a new-style class or not), how do you generate all the base classes – anywhere in the inheritance hierarchy – it issubclass of?

Asked By: Sridhar Ratnakumar



you can use the __bases__ tuple of the class object:

class A(object, B, C):
    def __init__(self):
print A.__bases__

The tuple returned by __bases__ has all its base classes.

Answered By: mandel

inspect.getclasstree() will create a nested list of classes and their bases.

inspect.getclasstree(inspect.getmro(IOError)) # Insert your Class instead of IOError.
Answered By: Ned Batchelder

See the __bases__ property available on a python class, which contains a tuple of the bases classes:

>>> def classlookup(cls):
...     c = list(cls.__bases__)
...     for base in c:
...         c.extend(classlookup(base))
...     return c
>>> class A: pass
>>> class B(A): pass
>>> class C(object, B): pass
>>> classlookup(C)
[<type 'object'>, <class __main__.B at 0x00AB7300>, <class __main__.A at 0x00A6D630>]
Answered By: Crescent Fresh

inspect.getmro(cls) works for both new and old style classes and returns the same as NewClass.mro(): a list of the class and all its ancestor classes, in the order used for method resolution.

>>> class A(object):
>>>     pass
>>> class B(A):
>>>     pass
>>> import inspect
>>> inspect.getmro(B)
(<class '__main__.B'>, <class '__main__.A'>, <type 'object'>)
Answered By: Jochen Ritzel

Although Jochen’s answer is very helpful and correct, as you can obtain the class hierarchy using the .getmro() method of the inspect module, it’s also important to highlight that Python’s inheritance hierarchy is as follows:


class MyClass(YourClass):

An inheriting class

  • Child class
  • Derived class
  • Subclass


class YourClass(Object):

An inherited class

  • Parent class
  • Base class
  • Superclass

One class can inherit from another
– The class’ attributed are inherited
– in particular, its methods are inherited
– this means that instances of an inheriting (child) class can access attributed of the inherited (parent) class

instance -> class -> then inherited classes


import inspect

will show you the hierarchy, within Python.

Answered By: Jenobi

In python 3.7 you don’t need to import inspect, type.mro will give you the result.

>>> class A:
...   pass
>>> class B(A):
...   pass
>>> type.mro(B)
[<class '__main__.B'>, <class '__main__.A'>, <class 'object'>]

attention that in python 3.x every class inherits from base object class.

Answered By: Serjik

According to the Python doc, we can also simply use class.__mro__ attribute or class.mro() method:

>>> class A:
...     pass
>>> class B(A):
...     pass
>>> B.__mro__
(<class '__main__.B'>, <class '__main__.A'>, <class 'object'>)
>>> A.__mro__
(<class '__main__.A'>, <class 'object'>)
>>> object.__mro__
(<class 'object'>,)
>>> B.mro()
[<class '__main__.B'>, <class '__main__.A'>, <class 'object'>]
>>> A.mro()
[<class '__main__.A'>, <class 'object'>]
>>> object.mro()
[<class 'object'>]
>>> A in B.mro()

Answered By: YaOzI