Q:

if there is an end for the command `dir(' '.__dir__.__dir__.__dir__.__dir__)` to stop printing its attributes?

Every object has a __dir__ attribute, will the command stop if extra .__dir__ references are appended?
>>> dir(''.__dir__)
['__call__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__text_signature__']

and,
>>> dir(''.__dir__.__dir__.__dir__.__dir__)
['__call__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__text_signature__']

will it stop when enough '.dir' are appended?

A:

You are taking the dir() of the __dir__ attribute, which is a builtin_function_or_method object, which has a __dir__ attribute. So yes, you can chain those __dir__ attribute lookups endlessly, because the result will always be the same; a bound method object:
>>> ''.__dir__.__dir__
<built-in method __dir__ of builtin_function_or_method object at 0x10672cfc0>
>>> ''.__dir__.__dir__.__dir__
<built-in method __dir__ of builtin_function_or_method object at 0x1067361f8>

Every object in Python has a __dir__ attribute, it is always a callable.
Note: the way you strung the attribute lookups keeps a chain of bound method objects alive, so you will eventually run out of memory; each __dir__ method wrapper references the preceding one in their __self__ attribute.

