How to step into another .py file while debugging in PyCharm

In my current project I have a script that contains the line:

exec(open(pathname/script.py).read())

Which is supposed to execute a file in another folder (but still contained within the Pycharm project root directory).

When I debug this script and get to the line above, clicking 'Step into' or 'Step into my code' does not take me into script.py. I guess this is not the right syntax to use in order to step into another script? What syntax should I use? Thanks