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

Posted by Minseok Kim
Minseok Kim
2,708 Points

Don't know how to do the sets challenge...

https://teamtreehouse.com/library/python-collections-2/sets/set-math

Challenge: Let's write some functions to explore set math a bit more. We're going to be using this COURSES dict in all of the examples. Don't change it, though!

So, first, write a function named covers that accepts a single parameter, a set of topics. Have the function return a list of courses from COURSES where the supplied set and the course's value (also a set) overlap.

For example, covers({"Python"}) would return ["Python Basics"].

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(a):
    list_1 = []
    for value in a:
        for courses in COURSES:
            if courses & value:
                list_1.append(courses)
    return list_1
Sam Wederell
Sam Wederell
20,276 Points
Sam Wederell
Sam Wederell
20,276 Points

You don't need to iterate through the supplied argument 'a'.

Minseok Kim
Minseok Kim
2,708 Points

Sam Wederell
then why doesnt this work?

def covers(a):
    list_1 = []
    for courses in COURSES:
        if courses & a:
            list_1.append(courses)
    print (list_1)
Sam Wederell
Sam Wederell
20,276 Points
Sam Wederell
Sam Wederell
20,276 Points

you're comparing the course objects rather than the values.

1 Answer

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

You're close, in your 2nd try, but there's two issues:

  • you need to test the associated set instead of the key ("if COURSES[courses] & a:")
  • you need to return the new list (and you won't need to "print" anything)