Can I get a reference to the 'owner' class during the __init__ method of a descriptor?

Question

Is it possible to access the \'owner\' class inside a descriptor during the __init__ function of that descriptor, without passing it in manually as in this example?

Answer 1

Since Python 3.6, you can use the __set_name__ special method:

class FooDescriptor(object):
    def __set_name__(self, owner, name):
        owner.foo = 42

class BarClass(object):
    foo_attribute = FooDescriptor()

# foo_attribute.__set_name__(BarClass, "foo_attribute") called after class definition

__set_name__ is automatically called on all descriptors in a class immediately after the class is created. See PEP 487 for more details.