Set Intersection Union

def main():
    set1 = {1, 2, 3, 3, 3, 2}
    print(set1)
    print('Length =', len(set1))
    set2 = set(range(1, 10))
    print(set2)
    set1.add(4)
    set1.add(5)
    set2.update([11, 12])
    print(set1)
    print(set2)
    set2.discard(5)
    # would rise KeyError if the to-remove element not exist 
    if 4 in set2:
        set2.remove(4)
    print(set2)
    # for loop all elements in set 
    for elem in set2:
        print(elem ** 2, end=' ')
    print()
    # transfer tuple to set 
    set3 = set((1, 2, 3, 3, 2, 1))
    print(set3.pop())
    print(set3)
    ### set calculation on union / intersection / difference / ...
    print(set1 & set2)
    # print(set1.intersection(set2))
    print(set1 | set2)
    # print(set1.union(set2))
    print(set1 - set2)
    # print(set1.difference(set2))
    print(set1 ^ set2)
    # print(set1.symmetric_difference(set2))
    # check subset and superset 
    print(set2 <= set1)
    # print(set2.issubset(set1))
    print(set3 <= set1)
    # print(set3.issubset(set1))
    print(set1 >= set2)
    # print(set1.issuperset(set2))
    print(set1 >= set3)
    # print(set1.issuperset(set3))

if __name__ == '__main__':
    main()