Working with collections

Python The set in is consistent with the set in mathematics , Duplicate elements are not allowed , And it can intersect 、 Combine 、 Subtraction and so on .

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)
    # remove If the element does not exist, it will trigger KeyError
    if 4 in set2:
        set2.remove(4)
    print(set2)
    #  Traverse the collection container 
    for elem in set2:
        print(elem ** 2, end=' ')
    print()
    #  Convert tuples into sets 
    set3 = set((1, 2, 3, 3, 2, 1))
    print(set3.pop())
    print(set3)
    #  Intersection of sets 、 Combine 、 Difference set 、 Symmetric difference operation 
    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))
    #  Judging subsets and supersets 
    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()

explain ：Python Allows some special methods to customize operators for certain types or data structures （ Later chapters will cover ）, In the above code, we can call the method of the collection object when we operate on the collection , You can also use the corresponding operator directly , for example & Operator with intersection The function of the method is the same , But using operators makes the code more intuitive .