project kudoSudoku follows SUDO project

[sylas]

When I run the project with "python kudoSudoku" I should like to have a non-stop project. With exit() in cop_class.py, I go out of the project, and then I run solver.py. But if I put "import solver" instead of "exit()" I cannot nomore import name 'sudoku'. Remember, at the top of solver.py there is: from kudoSudoku import sudoku.
Why with running solver.py alone there is no problem, but with my non-stop project , problem appears. I recognize I am lost with so many imports that exist. May be someone experienced in imports , finds a solution.