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

Leo Marco Corpuz
Leo Marco Corpuz
18,975 Points
Posted by Leo Marco Corpuz
Leo Marco Corpuz
18,975 Points

Common courses challenge

Here's my code. Any advice? Thanks!

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):
    common_list=[]
    for subject in COURSES:
        common_subject=topics.intersection(subject)
        common_list.append(common_subject)
    return common_list

1 Answer

Jeff Muday
MOD
Jeff Muday
Treehouse Moderator 28,722 Points
Jeff Muday
Jeff Muday
Treehouse Moderator 28,722 Points

Your approach definitely shows you know something about Python sets. Let's build on that.

  • I see you wanted common_list to be all courses matching your topics set.

Great idea, keep it.

  • You iterate through the COURSES set with a "for" loop.

Keep this idea-- but let's mod it slightly.

modification: you will want to use the COURSES.items() iterator. It's not the only way to do things, but it is advantageous because it returns BOTH the course_name and the course_topics. This is an important pattern Kenneth would like you to remember.

  • I like that you look for an intersection of topics -- well played, but let's change it a little.

modification: look for an intersection with course_topics instead.

  • I like you are doing the common_list.append. This is good, but we need to change it a little.

modification: Let's change it to ONLY append the course name when the length of the common_subject is greater than zero (which indicates our topics matched/intersected with course_topics. This will avoid us having empty sets appended to our list.

  • After the loop you return the common list. Well played, this is right.
def covers(topics):
    common_list=[]
    for course_name, course_topics in COURSES.items():
        common_subject=topics.intersection(course_topics)
        if len(common_subject) > 0:
            common_list.append(course_name)
    return common_list

Good luck on your Python journey. It can be a little frustrating at times, but pays off well!