Question

Suppose we have the following class hierarchy:

class ClassA:

    @property
    def foo(self): return "hello"

class ClassB(ClassA):

    @property
    def bar(self): return "world"

If I explore __dict__ on ClassB like so, I only see the bar attribute:

for name,_ in ClassB.__dict__.items():

    if name.startswith("__"):
        continue

    print(name)

Output is bar

I can roll my own means to get attributes on not only the specified type but its ancestors. However, my question is whether there’s already a way in python for me to do this without re-inventing a wheel.

def return_attributes_including_inherited(type):
    results = []
    return_attributes_including_inherited_helper(type,results)
    return results

def return_attributes_including_inherited_helper(type,attributes):

    for name,attribute_as_object in type.__dict__.items():

        if name.startswith("__"):
            continue

        attributes.append(name)

    for base_type in type.__bases__:
        return_attributes_including_inherited_helper(base_type,attributes)

Running my code as follows…

for attribute_name in return_attributes_including_inherited(ClassB):
    print(attribute_name)

… gives back both bar and foo.

Note that I’m simplifying some things: name collisions, using items() when for this example I could use dict, skipping over anything that starts with __, ignoring the possibility that two ancestors themselves have a common ancestor, etc.

EDIT1 – I tried to keep the example simple. But I really want both the attribute name and the attribute reference for each class and ancestor class. One of the answers below has me on a better track, I’ll post some better code when I get it to work.

EDIT2 – This does what I want and is very succinct. It’s based on Eli’s answer below.

def get_attributes(type):

    attributes = set(type.__dict__.items())

    for type in type.__mro__:
        attributes.update(type.__dict__.items())

    return attributes

It gives back both the attribute names and their references.

EDIT3 – One of the answers below suggested using inspect.getmembers. This appears very useful because it’s like dict only it operates on ancestor classes as well.

Since a large part of what I was trying to do was find attributes marked with a particular descriptor, and include ancestors classes, here is some code that would help do that in case it helps anyone:

class MyCustomDescriptor:

    # This is greatly oversimplified

    def __init__(self,foo,bar):
        self._foo = foo
        self._bar = bar
        pass

    def __call__(self,decorated_function):
        return self

    def __get__(self,instance,type):

        if not instance:
            return self

        return 10

class ClassA:

    @property
    def foo(self): return "hello"

    @MyCustomDescriptor(foo="a",bar="b")
    def bar(self): pass

    @MyCustomDescriptor(foo="c",bar="d")
    def baz(self): pass

class ClassB(ClassA):

    @property
    def something_we_dont_care_about(self): return "world"

    @MyCustomDescriptor(foo="e",bar="f")
    def blah(self): pass

# This will get attributes on the specified type (class) that are of matching_attribute_type.  It just returns the attributes themselves, not their names.
def get_attributes_of_matching_type(type,matching_attribute_type):

    return_value = []

    for member in inspect.getmembers(type):

        member_name = member[0]
        member_instance = member[1]

        if isinstance(member_instance,matching_attribute_type):
            return_value.append(member_instance)

    return return_value

# This will return a dictionary of name & instance of attributes on type that are of matching_attribute_type (useful when you're looking for attributes marked with a particular descriptor)
def get_attribute_name_and_instance_of_matching_type(type,matching_attribute_type):

    return_value = {}

    for member in inspect.getmembers(ClassB):

        member_name = member[0]
        member_instance = member[1]

        if isinstance(member_instance,matching_attribute_type):
            return_value[member_name] = member_instance

    return return_value

Answer 1

You should use python’s inspect module for any such introspective capabilities.

.
.
>>> class ClassC(ClassB):
...     def baz(self):
...         return "hiya"
...
>>> import inspect
>>> for attr in inspect.getmembers(ClassC):
...   print attr
... 
('__doc__', None)
('__module__', '__main__')
('bar', <property object at 0x10046bf70>)
('baz', <unbound method ClassC.baz>)
('foo', <property object at 0x10046bf18>)

Read more about the inspect module here.