a
|-__init__.py
|-b
|---__init__.py
|---c.py

>>> import a.b.c as c

>>> from a import b

>>> from a.b import c
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: cannot import name 'c'
cannot import name 'c'

>>> from a.b.c import d
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named 'a.b.c'
No module named 'a.b.c'