If you want to loop thru several files you could think about something like in these examples or you would have to do some other combinations of nodes before and after the python node. Might involve some planning.
There are tons of python courses and introductions out there but ones that do really explain what is going on and why are hard to come by. And then there are very advanced courses with statistical stuff that first throw a bunch of formulas at you and then let you figure out the code by yourself basically.
For machine learning and python the best site and books I have come by is
Which gives you working code samples and explainaitions taylored to the task at hand. Of course there is always more to learn and it might not be a general introduction into Python.
About that, one idea if not the most creative one is to take the Kaggle self study course:
And then the actual NSA has produced a python course that seems pretty good especially covering a lot of relevant issues, but I have yet to see someone bring that into an actual jupyter notebook instead of a scanned PDF.
https://www.google.com/search?q=nsa+python+tutorial&ie=UTF-8&oe=UTF-8&hl=de-us&client=safari
And depending on how you like to study, a video course from Udemy or an old fashioned book might be suitable for you.