python import module from a package

Question

folder structure:

   main.py
   packages 
      __init__.py
      mod.py

main py:

Answer 1

See also: In Python, what exactly does “import *” import?

adding __all__ to packages.__init__:

__all__ = ['mod']
from packages import *

and module 'mod' will be imported, else 'mod' is not in the namespace of 'packages', but I can not explain why 'import *' without __all__ do not import 'mod'.