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Python Python Collections (2016, retired 2019) Sets Set Math

My code seems to work perfectly in workspaces when tested, but the challenge says it is returning incorrect values.

My code seems to be accurately returning a list of classes that cover the topics in the given set when run in workspaces, but when run it the challenge it does not pass. What am I missing?

    "Python Basics": {"Python", "functions", "variables",
                      "booleans", "integers", "floats",
                      "arrays", "strings", "exceptions",
                      "conditions", "input", "loops"},
    "Java Basics": {"Java", "strings", "variables",
                    "input", "exceptions", "integers",
                    "booleans", "loops"},
    "PHP Basics": {"PHP", "variables", "conditions",
                   "integers", "floats", "strings",
                   "booleans", "HTML"},
    "Ruby Basics": {"Ruby", "strings", "floats",
                    "integers", "conditions",
                    "functions", "input"}

def covers(topics):
    courses_covering = []

    for course in COURSES:
        if topics.issubset(COURSES[course]):

    return courses_covering

4 Answers

Here's a hint:

You can to use intersection instead of checking if a set is a sub set of another.

Ok I may really be missing something, but I get the same error with the following code which uses the difference operator:

def covers(topics): courses = []

for key, value in COURSES.items():
    if len(topics - value) == 0:

return courses

and I also tried the following function that uses intersection:

def covers(topics): courses = []

for key, value in COURSES.items():
    if topics.intersection(value) == topics:

return courses

neither of these passed.

implse finite
implse finite
3,106 Points


here's my solution, maybe not the best :

def covers(a):
    result = []
    for k, v in COURSES.items():
        b = COURSES[k]
        c = a.intersection(b)
        if len(c) != 0:
    return result

Thank you everyone for your help. I see my problem now. I was actually solving the next step in the challenge. I thought that every topic in the given set had to be covered in the class, which is not the case. Well, at least I found three different ways to solve the next problem.