Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

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

Vuk Spasojevic
Vuk Spasojevic
9,491 Points
Posted by Vuk Spasojevic
Vuk Spasojevic
9,491 Points

Why this is not working?

Please help me understand where I am doing wrong.

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):
    courses_list = []    
    for course in COURSES:
        if COURSES[course] & topics:   # Here the & sign finds the overlaps of the two sets.
            courses_list.append(course)
    return courses_list

def covers_all(topics):
    courses_list =[]
    for key, value in COURSES.items():
        if COURSES[key] & topics:
            course_list.append(key)
    return courses_list

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,441 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,441 Points

Your two functions are doing the same thing. In fact, all three of the code snippets below are equivalent:

    # using the default keys
    for course in COURSES:
        if COURSES[course] & topics:
            courses_list.append(course)

    # using explicit keys
    for key in COURSES.keys():
        if COURSES[key] & topics:
            courses_list.append(course)

    # getting keys and values, using only keys
    for key, value in COURSES.items():
        if COURSES[key] & topics:
            course_list.append(key)

The goal of the second task is to find the more restrictive solution where topics is a proper subset of the courses topics and not simply has an overlap. Try using the issubset method.