How to get the parents of a Python class?

Question

How can I get the parent class(es) of a Python class?

Answer 1

If you want all the ancestors rather than just the immediate ones, use inspect.getmro:

import inspect
print inspect.getmro(cls)

Usefully, this gives you all ancestor classes in the "method resolution order" -- i.e. the order in which the ancestors will be checked when resolving a method (or, actually, any other attribute -- methods and other attributes live in the same namespace in Python, after all;-).

Answer 2

If you want to ensure they all get called, use super at all levels.

Answer 3

Use bases if you just want to get the parents, use __mro__ (as pointed out by @naught101) for getting the method resolution order (so to know in which order the init's were executed).

Bases (and first getting the class for an existing object):

>>> some_object = "some_text"
>>> some_object.__class__.__bases__
(object,)

For mro in recent Python versions:

>>> some_object = "some_text"
>>> some_object.__class__.__mro__
(str, object)

Obviously, when you already have a class definition, you can just call __mro__ on that directly:

>>> class A(): pass
>>> A.__mro__
(__main__.A, object)

Answer 4

The FASTEST way, to see all parents, and IN ORDER, just use the built in __mro__

i.e. repr(YOUR_CLASS.__mro__)

---

>>>
>>>
>>> import getpass
>>> getpass.GetPassWarning.__mro__

outputs, IN ORDER

---

(<class 'getpass.GetPassWarning'>, <type 'exceptions.UserWarning'>,
<type 'exceptions.Warning'>, <type 'exceptions.Exception'>, 
<type 'exceptions.BaseException'>, <type 'object'>)
>>>

---

There you have it. The "best" answer right now, has 182 votes (as I am typing this) but this is SO much simpler than some convoluted for loop, looking into bases one class at a time, not to mention when a class extends TWO or more parent classes. Importing and using inspect just clouds the scope unnecessarily. It honestly is a shame people don't know to just use the built-ins

I Hope this Helps!

Answer 5

New-style classes have an mro method you can call which returns a list of parent classes in method resolution order.

Answer 6

Use the following attribute:

cls.__bases__

From the docs:

The tuple of base classes of a class object.

Example:

>>> str.__bases__
(<type 'basestring'>,)

Another example:

>>> class A(object):
...   pass
... 
>>> class B(object):
...   pass
... 
>>> class C(A, B):
...   pass
... 
>>> C.__bases__
(<class '__main__.A'>, <class '__main__.B'>)