How to generate a random string and use it in a different def funtion in Python?

I'm trying to create a piece of code that will generate a random string of characters (upper, lower, digits, and certain symbols) before giving the string a score, and displaying them both. I have created the rating algorithm, but the generation algorithm is giving me some trouble. Here's what I have so far:

def genString():
    leng = random.randint(8, 12)
    chars = string.ascii_letters + string.digits + "!$%^&*()-_=+"
    gend = "".join(random.choice(chars) for n in range(leng))
    stringEntry.config(text = gend)
    rateString()

In theory, this would modify an entrybox in my Tkinter GUI with the string, before rating it as if the user entered it themselves.

How would I go about making this work?