set math

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(p):
    ret = []
    for k, v in COURSES.items():
        setv = set(v)
        if p.intersection(setv):
            ret.append(k)
    return ret

def covers_all(topics):
    all_courses = []
    for keys, values in COURSES.items():
        if values.issubset(topics):
            all_courses.append(key)
    return all_courses 
covers_all()