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

Posted by Michael Aronian
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Michael Aronian
Python Web Development Techdegree Student 5,453 Points

I can't seem to get this one right

I can't find the right code for this one.

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(arg):
    course = []
    for key, value in COURSES.items():
        if value & arg:
            course.append(key)
    return course

def covers_all(*arg):
    course = []
    for key, value in COURSES.items():
        if value.issuperset(arg):
             course.append(key)
    return course

2 Answers

Pete P
Pete P
7,613 Points
Pete P
Pete P
7,613 Points

Worked for me after removing the asterisk from *arg.

Hopefully someone can clarify this better, but I believe *arg is used when you are passing an unknown amount of arguments to a function that is prepared to unpack them. Right now whatever set is being passed into your function gets unpacked into a tuple with the set being the only element of that tuple.

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

Pete P's answer is close enough to be correct. In short, the parameter and its use as an argument to issubset() need to agree: either both have an asterisk or neither. This way it's either a single variable received and used or a tuple received and unpacked for use. 

# without asterisks 
def covers_all(arg):
    course = []
    for key, value in COURSES.items():
        if value.issuperset(arg):
             course.append(key)
    return course

# or with asterisks
def covers_all(*arg):
    course = []
    for key, value in COURSES.items():
        if value.issuperset(*arg):
             course.append(key)
    return course
Pete P
Pete P
7,613 Points
Pete P
Pete P
7,613 Points

Thanks for clarifying that Chris! As always, much appreciated.