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Python Python Collections (2016, retired 2019) Dictionaries Teacher Stats

James Dunn
James Dunn
3,041 Points

Why is this producing the wrong result?

Once again I'm lost. I know for a fact that stats() produces the a list of lists. And that the lists are formatted as such [teacher_name, number_of_courses], as is required by the challenge.

However, when I plug it into the challenge it says that it isn't producing the correct results.

Any help would be much appreciated.

Thank you.

teachers.py
# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.
def num_teachers(my_dict):
    num_of_teachers = 0

    for key in my_dict:
        num_of_teachers += 1
    return num_of_teachers
#End of num_teachers

def num_courses(my_dict):
    num_of_courses = 0

    for value in my_dict.values():
        for item in value:
            num_of_courses += 1
    return num_of_courses


def courses(my_dict):
    course_list = []

    for value in my_dict.values():
        for item in value:
            course_list.append(item)
    return course_list

def most_courses(my_dict):
    answer = ""
    max_val = 0
    dict_items = None
    teacher = ""
    i = 0

    for key in my_dict.keys():
        for item in my_dict.values():
            dict_items = item

            for value in dict_items:
                i += 1

        if i > max_val:
            max_val = i
            teacher = key
        elif i == max_val:
            teacher = teacher + "&" + key       

    return teacher


def stats(my_dict):
    answer = []
    stat = []
    course_cnt = 0

    for key in my_dict.keys():
        for course in my_dict.values():
            course_cnt += 1

        stat = [key, course_cnt]
        course_cnt = 0
        answer.extend(stat)

    return answer

2 Answers

Louise St. Germain
Louise St. Germain
19,412 Points

Hi James,

You're very close! There are two minor things to fix, and then it should work properly.

First, for this line:

for course in my_dict.values():

my_dict.values() contains a list of lists (i.e., a list of all the values, which are themselves lists), so while you're expecting it to be looping through all the items in the list that goes with that key, what it's actually doing is looping through its higher-level list, i.e., at the teacher level. So essentially it's counting the total number of teachers, not the total number of courses for a given teacher.

If you change that line to this, it should work properly:

for course in my_dict[key]:

Second, you correctly create a list with the teacher and their stat, but when you extend the answer list, it creates one big continuous list, instead of a list of lists. Your code is outputting something like,

['Kenneth Love', 3, 'Andrew Chalkley', 2, 'Craig Dennis', 5]

instead of:

[['Kenneth Love', 3], ['Andrew Chalkley', 2], ['Craig Dennis', 5]]

If you use append instead of extend, that should fix the problem.

answer.append(stat)

With those two little things, I think you should be able to finish the challenge. I hope this helps!

James Dunn
James Dunn
3,041 Points

Thanks! That took care of the problem.