SET

Set Methods and Useful Built-in Functions

Set

• Set: object that stores a collection of data in same way as mathematical set
    • All items must be unique
    • Set is unordered
    • Elements can be of different data types
• len function: returns the number of elements in the set
• Sets are mutable objects
• add method: adds an element to a set
• update method: adds a group of elements to a set
    • Argument must be a sequence containing iterable elements, and each of the elements is added to the set
• remove and discard methods: remove the specified item from the set
    • The item that should be removed is passed to both methods as an argument
    • Behave differently when the specified item is not found in the set
    • remove method raises a KeyError exception
    • discard method does not raise an exception
• clear method: clears all the elements of the set

FINDING THE UNION OF SETS

• Union of two sets: a set that contains all the elements of both sets
• To find the union of two sets:
    • Use the union method
    • Format: set1.union(set2)
    • Use the | operator
    • Format: set1 | set2
    • Both techniques return a new set which contains the union of both sets

FINDING THE INTERSECTION OF SETS

• Intersection of two sets: a set that contains only the elements found in both sets
• To find the intersection of two sets:
    • Use the intersection method
    • Format: set1.intersection(set2)
    • Use the & operator
    • Format: set1 & set2
    • Both techniques return a new set which contains the intersection of both sets

FINDING THE SYMMETRIC DIFFERENCE OF SETS

• Symmetric difference of two sets: a set that contains the elements that are not shared by the two sets
• To find the symmetric difference of two sets:
    • Use the symmetric_difference method
    • Format: set1.symmetric_difference(set2)
    • Use the ^ operator
    • Format: set1 ^ set2

FINDING SUBSETS AND SUPERSETS

• Set A is subset of set B if all the elements in set A are included in set B
• To determine whether set A is subset of set B
    • Use the issubset method
    • Format: setA.issubset(setB)
    • Use the <= operator
    • Format: setA <= setB
• Set A is superset of set B if it contains all the elements of set B
• To determine whether set A is superset of set B
    • Use the issuperset method
    • Format: setA.issuperset(setB)
    • Use the >= operator
    • Format: setA >= setB

SET OPERATION