How to get the parents of a Python class?
Question:
How can I get the parent class(es) of a Python class?
Answers:
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'>)
If you want all the ancestors rather than just the immediate ones, use cls.__mro__.
For versions of Python earlier than 3.5, 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;-).
If you want to ensure they all get called, use super at all levels.
New-style classes have an mro method you can call which returns a list of parent classes in method resolution order.
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)
The fastest way to get all parents, and in order, is to just use the __mro__ built-in.
For instance, repr(YOUR_CLASS.__mro__).
The following:
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 may have more votes 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.
This funciton will print the all the classes of an object, while in each step the next object will the left most parent.
def print_root_left(class_):
while True:
print(class_)
# Check there if are no bases then we have reached the root class
if not class_.__bases__:
break
class_=class_.__bases__[0] # use the left most parent
example = "hello"
print_root_left(example.__class__)
If you have a variable and want to get its class and parent classes use type() method which will give class for a variable
val="happy coding"
print(type(val).__mro__)
Output:
(<class 'str'>, <class 'object'>)
How can I get the parent class(es) of a Python class?
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'>)
If you want all the ancestors rather than just the immediate ones, use cls.__mro__.
For versions of Python earlier than 3.5, 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;-).
If you want to ensure they all get called, use super at all levels.
New-style classes have an mro method you can call which returns a list of parent classes in method resolution order.
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)
The fastest way to get all parents, and in order, is to just use the __mro__ built-in.
For instance, repr(YOUR_CLASS.__mro__).
The following:
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 may have more votes 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.
This funciton will print the all the classes of an object, while in each step the next object will the left most parent.
def print_root_left(class_):
while True:
print(class_)
# Check there if are no bases then we have reached the root class
if not class_.__bases__:
break
class_=class_.__bases__[0] # use the left most parent
example = "hello"
print_root_left(example.__class__)
If you have a variable and want to get its class and parent classes use type() method which will give class for a variable
val="happy coding"
print(type(val).__mro__)
Output:
(<class 'str'>, <class 'object'>)