tester
├── __init__.py
├── first_level.py
└── sub
    ├── __init__.py
    └── second_level.py

# first_level.py
print "This is the first level of the package"

# sub/second_level.py
import ..first_level
print "This is the second level"

Python 2.7.3 (default, Aug  1 2012, 14:42:42)
[GCC 4.2.1 Compatible Apple Clang 4.0 ((tags/Apple/clang-421.0.57))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
Welcome!
>>> import tester
>>> import tester.sub.second_level
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "tester/sub/second_level.py", line 1
    import ..first_level
           ^
SyntaxError: invalid syntax