I have a directory structure like this

project/
        __init__.py
        greetings.py
        script.py

greetings.py

def hello():
    print('Hello')

script.py

from . import greetings

greetings.hello()

When I execute python script.py following error occurs

Traceback (most recent call last):
  File "script.py", line 1, in <module>
    from . import greetings
ImportError: cannot import name 'greetings'

If I just use import greetings in script.py everything works. But why does the relative import give error? And why does it work when I use from . import models in views while working in django.