Set Methods and Operations

Understanding Sets

A set in Python is an unordered collection of unique elements. It’s defined by curly braces {} and elements are separated by commas. Sets are mutable, meaning you can add or remove elements after creation.

Example:

Python

my_set = {1, 2, 3, 4}

Set Methods

Python provides several methods to manipulate sets:

Adding and Removing Elements

• add(element): Adds an element to the set.
• remove(element): Removes an element from the set. Raises a KeyError if the element is not present.  
• discard(element): Removes an element from the set if it is present. Does nothing if the element is not present.
• pop(): Removes and returns an arbitrary element from the set.
• clear(): Removes all elements from the set.

Example:

Python

my_set = {1, 2, 3}
my_set.add(4)  # {1, 2, 3, 4}
my_set.remove(2)  # {1, 3, 4}
my_set.discard(5)  # No error
my_set.pop()  # Removes a random element
my_set.clear()  # Empty set

Set Operations

• union(other_set): Returns a new set containing all unique elements from both sets.
• intersection(other_set): Returns a new set containing elements present in both sets.
• difference(other_set): Returns a new set containing elements in the current set but not in the other set.
• symmetric_difference(other_set): Returns a new set containing elements in either set, but not both.
• update(other_set): Modifies the current set by adding elements from the other set.
• intersection_update(other_set): Modifies the current set to contain only the intersection of both sets.
• difference_update(other_set): Modifies the current set to contain only the difference between the two sets.
• symmetric_difference_update(other_set): Modifies the current set to contain the symmetric difference of both sets.

Example:

Python

set1 = {1, 2, 3}
set2 = {2, 3, 4}

union_set = set1.union(set2)  # {1, 2, 3, 4}
intersection_set = set1.intersection(set2)  # {2, 3}
difference_set = set1.difference(set2)  # {1}
symmetric_difference_set = set1.symmetric_difference(set2)  # {1, 4}

set1.update(set2)  # set1 becomes {1, 2, 3, 4}

Other Useful Methods

• copy(): Returns a shallow copy of the set.
• issubset(other_set): Returns True if all elements in the current set are also in the other set.
• issuperset(other_set): Returns True if all elements in the other set are also in the current set.
• isdisjoint(other_set): Returns True if the two sets have no elements in common.

Set Operators

• |: Union operator
• &: Intersection operator
• -: Difference operator
• ^: Symmetric difference operator

Example:

Python

set1 = {1, 2, 3}
set2 = {2, 3, 4}

union_set = set1 | set2  # {1, 2, 3, 4}
intersection_set = set1 & set2  # {2, 3}
difference_set = set1 - set2  # {1}
symmetric_difference_set = set1 ^ set2  # {1, 4}

By understanding these methods and operators, you can effectively work with sets in Python and perform various set operations.

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