Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

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

Joseph Ferrero
Joseph Ferrero
1,308 Points

Hello, Can someone explain why this doesnt work? I'm not really sure what else to do. Thanks, Joseph Ferrero

Just need some help

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):
    overlap = []
    for course in courses:
        overlap.append(topics.intersection(course))
    return overlap

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 67,989 Points

Let's look at what your code is doing:

def covers(topics):
    overlap = []  # initialize list
    for course in courses:  # "courses" is not defined. Did you mean COURSES
        # 'course' here is each of the dictionary keys
        overlap.append(topics.intersection(course))  # intersecting topics set with course name (string)
    return overlap

Running this in the REPL returns four empty sets: [set(), set(), set(), set()]

Try these:

  • In for loop, change "courses" to COURSES
  • look at both the key and value using: for course_name, course_topics in COURSES.items():
  • perform intersection between topics and course_topics
  • append course_name