Python set tutorial with examples

Collection of unordered and unindexed elements. No duplicate element is allowed.
Example : set of user IDs of any club membership, there can't be any duplicate values, they are not in any order and there is no indexing

Declaring a set

my_set={'Alex','Ronald','John'}
print(my_set)

Output

{'Alex', 'Ronald', 'John'}

Blank Set

my_set=set() # declaring a blank set
my_set.add('alex') # adding element 
print(my_set)

We can't dsiplay elements based on position as set is unindexed.

my_set={"Alex","Ronald","John"}
print(my_set[1])

Above code will generate error

Python data structure using set an unordered unindexed and unique elements, methods and functions

Displaying all items by looping

We used for loop to display all items of the set.

my_set={'Alex','Ronald','John'}
for i in my_set:
    print(i)

Output is here

Alex
Ronald
John

Searching element

my_set={'Alex','Ronald','John'}
if 'John' in my_set:
 print("Yes, Present in set")
else:
 print("No , not present in set")

Output is here

Yes, Present in set

Set Operations in Python


union()	intersection()	difference()	symmetric_difference()
A={1,2,3} B={3,4,5}	A={1,2,3} B={3,4,5}	A={1,2,3} B={3,4,5}	A={1,2,3} B={3,4,5}
A \| B A.union(B)	A & B A.intersection(B)	A - B A.difference(B)	A ^ B A.symmetric_difference(B)
{1, 2, 3, 4, 5}	{3}	{1, 2}	{1, 2, 4, 5}

Python set operations union, intersection, difference, symmetric_difference & updating the main set

Add , remove , update elements

Methods of set object

Method	Description
add(x)	Add element x to the set
update(x)	Add iterable elements of x to the set
clear()	Removes all elements of the set
copy()	Creating a copy of the set
discard()	Remove element from the set
isdisjoint()	Check for presence of common element
issubset()	Check for presence of all elements
issuperset()	Check for presence of all elements
pop()	Remove random element from the set
remove()	Remove element from the set

Number of elements in the set

len() returns number of elements present in a set

my_set={'Alex','Ronald','John'}
print("Number of elements: ",len(my_set))

Output is here

Number of elements: 3

len(), max(),min(),sum()

my_set={5,3,7,9,4}
print("Maximum value : ",max(my_set))
print("Minimum value : ",min(my_set))
print("Number of elements : ",len(my_set))
print("Sum of elements : ",sum(my_set))

Output

Maximum value :  9
Minimum value :  3
Number of elements :  5
Sum of elements :  28

Deleting set

my_set={'Alex','Ronald','John'}
del my_set
print("Number of elements: ",len(my_set))

The last line will create error as we are deleting the set before this line.

Joint two sets by union()

We will use union() mehtod to join two sets and print final array

my_set1={'Alex','Ronald','John'}
my_set2={'Ron','Geek'}
my_set=my_set1.union(my_set2)
print(my_set)

Output is here

{'Ronald', 'Geek', 'Alex', 'John', 'Ron'}

We can use difference() to find out difference of first and second array with respect to first array.

my_set1={'Alex','Ronald','John'}
my_set2={'Ron','Ronald'}
my_set=my_set1.difference(my_set2)
print(my_set)

Output is here

{'John', 'Alex'}

We can use intersection() to get common element between two or more sets

my_set1={'Alex','Ronald','John'}
my_set2={'Ron','Alex'}
my_set=my_set1.intersection(my_set2)
print(my_set)

Output is

{'Alex'}

With three sets

my_set1={'a','b','c'}
my_set2={'d','b','a'}
my_set3={'f','b','a'}
my_set=my_set1.intersection(my_set2,my_set3)
print(my_set)

Output

{'b', 'a'}

intersection_update() only keeps common elements and removes other.

my_set1={'Alex','Ronald','John'}
my_set2={'Ron','Ronald'}
my_set1.intersection_update(my_set2)
print(my_set1)

Output is here

{'Ronald'}

issubset() returns true if all elements are present inside another set.

my_set1={'a','b','c'}
my_set2={'d','b','a','f','c'}
my_set=my_set1.issubset(my_set2)
print(my_set)

Output

True

issuperset() To get true if all elements of subset present in main set.

my_set1={'d','b','a','f','c'}
my_set2={'a','b','c'}
my_set=my_set1.issuperset(my_set2)
print(my_set)

Output

True

All list methods Questions on set

tuple list Dictionary Python- Tutorials

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

About the author Watch on YouTube

Connect: