python - Why does cls.__name__ not appear in dir()?

Question

Let's say I have a simple class:

class Foobar(object):
    pass

If I use dir(Foobar), I'll get the following output:

['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']

Even though it does not appear in the output of dir(), I can access __name__:

Foobar.__name__

and get Foobar.

Why does Python behave that way?

Answer 1

dir is not guaranteed to return all possible attributes. From the docs:

Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases. For example, metaclass attributes are not in the result list when the argument is a class.