spam_relative.py

    # most of the time, don't use dots at all:
    from spam import eggs
    # If Python has trouble finding spam and spam.py is in the same directory:
    # (i.e. "package" as the code doing the import):
    from .spam import eggs
    # when spam.py is in the *enclosing* package, i.e. one level up:
    from ..spam import eggs
    # ImportError! At least in Python 3, you can only use the dots with
    # the `from a import b` syntax:
    import .spam