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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 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 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.