Python function to calculate the star rating from a given list of ratings

calculate_star_rating.py

def calculate_star_rating(ratings):
    """This function calculates the star rating of the given list with array positions as
    0 - 1 Star
    1 - 2 Stars
    2 - 3 Stars
    3 - 4 Stars
    4 - 5 Stars
    """
    stars = [1,2,3,4,5]
    return round(sum(list(map(lambda a,b: a*b, stars, ratings))) / sum(ratings), 2)

ratings = [100,200,300,400,500]
calculate_star_rating(ratings)
#3.67

Thats not clear code.

Your function got ratings but not used