although there are many posts on the internet as well as some posts on stack overflow, I still want to ask about this nasty python "import" problem.
OK. so, the open source code organization is usually like this:
project/src/model.py;
project/test/testmodel.py
if I put the famous __init__.py in project directory and also in src/ and test/ subdirectories, 
and then put "from project.src import model" for the testmodel.py. 
it does not work! keep telling me that the Module named "project.src" is not found!
how can I solve the problem without changing the code structure?
The directory where project is located is probably not in your python path.
python import problem