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

Jordon Crichton
Jordon Crichton
1,868 Points
Posted by Jordon Crichton
Jordon Crichton
1,868 Points

I wrote code that works in the console but produces an error in the challenge saying " Not the right output"

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"].

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(set):
    course_cover=[]
    for cover in COURSES.keys():
        if set & COURSES[cover] == set:
            course_cover.append(cover)
    return course_cover

2 Answers

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

Your test is a bit too specific. The union (&) by itself will detect an overlap, but by comparing that result to the original argument, you are further restricting it to a subset. That's not quite what the challenge is asking for in this task.

Bonus hint: You might keep it in mind for the next task.

Jordon Crichton
Jordon Crichton
1,868 Points
Jordon Crichton
Jordon Crichton
1,868 Points

I fixed it with len(set & COURSES[cover]) == 0 then continue else append the cover. However, is there another way to use a null set in an argument.

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

You could have just left off the equality comparison and used "set & COURSES[cover]" as the whole expression. When the result is empty, it's considered "falsey" by Python, and if it contains anything it is "truthy".