How Can We Determine Whether an Attribute belongs to the Instance or to the Class?

Question

Intro

In Python I want to get a list of all attributes of an object which belong to the class and not to the instance (a list of all static attributes).

---

Some code to test potential solutions with:

class Klass:

    static_var = 'static_var string'

    def __init__(self):
        self.instance_var = 'instance_var string'

    def instance_method(self, *args, **kwargs):
        pass

    @staticmethod
    def static_method(*args, **kwargs):
        # can be passed almost anything and ignores it.
        pass

obj = Klass()

---

Failed attempts:

At first I tried the following:

def class_attrs_which_are_not_instance_attrs(obj):
    return set(set(type(obj).__dict__) - set(obj.__dict__))

However, obj.__dict__ is empty, so the function is returning only type(obj).__dict__

Some things I noted:

dir(type(obj)) == dir(obj)

type(obj).__dict__ ⊆ dir(type(obj))

Answer 1

Code

Here is my solution:

def static_attributes(obj):
    """
    Generator to return a list of names and attributes which are
    class-level variables or static methods
    """
    klass = type(obj)
    for name, attribute in klass.__dict__.items():
        if not name.startswith('__') and \
                (type(attribute) in {staticmethod, classmethod} or not callable(attribute)):
            yield name, attribute

for name, attribute in static_attributes(obj):
    print(name)

Output

static_var
static_method

Discussion

• This generator function yields a list of name and attributes that are either staticmethod, classmethod, or class-level variables.
• I also filtered out those names that starts with dunder (such as __doc__)