Teacher Stats step 4 explanation

I've been using Jupyter Notebook to help me write notes and test out the challenge questions. The code below served as my solution to step 4. In the code, I commented out a line and it worked as a solution here, however, in Jupyter I need the line of code for the function to work properly.

I'd really appreciate if anyone could explain to me why that is.

If anyone has a better solution to this problem, I'd love to see it. I'm trying to get into the headspace that there's more than one way to tackle a problem. It would be great to learn a new way of thinking when it comes to programming with Python.

def most_courses(dict):
    teacher = ''
    max_count = 0

    for t,c in dict.items():
        if len(c) > max_count:
            teacher = t
            #max_count += len(c)
    return teacher