I have a python project looks like this:
src
 |
 +---- __init__.py
 |
 +---- branch2
         |
         +----__init__.py
         +----xx.py
 |
 +---- branch3
         |
         +---- __init__.py
         +---- yy.py
I want to import a python file in yy.py from a sibling package:
from branch2 import xx
but I got error:
ImportError: No module named xx
I'm sure that every package has a init.py file ,and my python version is 2.7.10