if __name__ == '__main__':
from a import dummy1
from b import dummy2
running python c.py will do what you want.
usualy you need to be sure that import didn't fail and use exception but probably this will be later when you will feel confortable enought with python.
Edit: two things:
- change url to point to your python version instead of 2.6.6
- i assume you don't ask about something like call, eval, exec( see the docs for details)