Not getting correct output

Question

Could anyone please help me with finishing this challenge, I really don't know what else to do. Thank you!

sets.py

COURSES = {
    "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):
    results = []
    for course, course_topics in COURSES.items():
        results.append(topics.intersection(course))
         # course_topics is the set which you can use for this question
    return results

Answer 1 · 2017-01-18T05:17:11Z

January 18, 2017 5:17am

Alex:

I'm sure there are a number of ways to complete this task and it looks like you are on the right path. The problem is that each time through the loop your code is appending to the results[] list you set up. So if you passed in a set with one element like: topics = {"Python"}, the code would produce this result.

[set(), set(), {"Python"}, set()]

NOTE that the ordering may be slightly different each time you run the code because dictionaries store their elements unordered.

Because you are appending to the list for each course in the dictionary (Python Basics, Java Basics...) you get four values in your list. The set() values above represent empty sets that are returned from your loop where "Python" did not match any value in the course_topics set.

What you need to do is add a conditional to only append when a non-empty set is returned. For instance.

def covers(topics):
    results = []
    for course, course_topics in COURSES.items():
        match_set = topics.intersection(course_topics)
        # only append to results[] if the returned set is not empty
        if len(match_set):
            results.append(course)
    return results

Answer 2 · 2017-01-18T05:07:25Z

January 18, 2017 5:07am

Hi Alex, you are looking to see which courses contain any of the topics (using intersection), which is great. However, you have to add the course to the results list and not the topics in the sets. The code below can be shortened, but I think it's easier to understand as is.

def covers(topics):
    results = []
    for course, course_topics in COURSES.items():
        overlap = topics.intersection(course_topics)
        if overlap:
            results.append(course)
    return results

Welcome to the Treehouse Community

Looking to learn something new?

Alex Diaz

Alex Diaz

Not getting correct output

2 Answers

jonlunsford

jonlunsford

Umesh Ravji

Umesh Ravji