Python Set Functions

Pradeep

Python Set Functions

This page will specifically cover available built-in Python functions which helps in performing variety of operations(such as adding, modifying & deleting items) on set objects. Please visit this page to understand Python Set in detail.

➠ Most of the Set functions available in Python are listed below, click on the required function to get more detail and sample examples.

Length/Size
Add
Update
Remove
Discard
Pop
Copy
Clear
issubset
issuperset
union
difference
difference_update
intersection
intersection_update
isdisjoint
symmetric_difference
symmetric_difference_update

Size / Length of Set: len() function can be used to get the number of items present in the input set.
```
Syntax: len(set_object)
```
- Example 1: Statement will return 5 as there are 5 items present in the set.
```
set_1 = {1, 2, 3, 6, 'A'}
len(set_1)

Output: 5
```
- Example 2: This will return Zero(0) as there is no item present in the set.
```
set_1 = set()
len(set_1)

Output: 0
```
Add item to Set: add() function will add the input value to the set.
```
Syntax: set_object.add(value)
```
- Example 1: Statement will add value 'C' to the set.
```
set_1 = {1, 2, 3, 6, 'A'}
set_1.add('C')
print(set_1)

Output: {1, 2, 3, 6, 'A', 'C'}
```
  Visit this page to understand difference between add and update functions
Update Set: update() function requires iterable object(such as string, list, set) as input otherwise it will throw error. Function will iterate through all the elements in the input object and add them as individual item in the existing set.
```
Syntax: set_object.extend(object)
```
- Example 1: Statement will fail as integer values are not iterable.
```
set_1 = {1, 2, 3, 6, 'A'}
set_1.update(4)
print(set_1)

Output: TypeError: 'int' object is not iterable
```
- Example 2: Statement will iterate thru input object list "['C', 'D']" and add each item in input list as individual item at the end of the main set.
```
set_1 = {1, 2, 3, 6, 'A'}
set_1.update(['C','D'])
print(set_1)

Output: {1, 2, 3, 6, 'A', 'D', 'C'}
```
- Example 3: Statement will iterate thru input string 'DBMS' and add each character in the input string as individual item at the end of the set.
```
set_1 = {1, 2, 3, 6, 'A'}
set_1.update('DBMS')
print(set_1)

Output: {1, 2, 3, 'B', 6, 'A', 'D', 'S', 'M'}
```
  Visit this page to understand difference between add and update functions
Remove item from Set: remove() function can be used to remove input item from the set. Function will throw error if value is not present in the set.
```
Syntax 1: set_object.remove(value)
```
- Example 1: Statement will fail as value 'd' is not present in the set.
```
set_1 = {'a', 'b', 'f', 'h', 'j'}
set_1.remove('d')

Output: KeyError: 'd'


Solution: Check if value is present before running remove function
if 'd' in set_1:
    set_1.remove('d')
```
- Example 2: Statement will remove 'b' item from the set.
```
set_1 = {'a', 'b', 'f', 'h', 'b', 'j'}
set_1.remove('b')
print(set_1)

Output: {'a', 'f', 'j', 'h'}
```
  Visit this page to understand difference between remove, discard and pop functions
Discard item from Set: discard() function can be used to remove input item from the set. Function will not throw error if value is not present in the set.
```
Syntax 1: set_object.discard(value)
```
- Example 1: Statement will fail as value 'd' is not present in the set.
```
set_1 = {'a', 'b', 'f', 'h', 'j'}
set_1.discard('d')

Output: None
```
- Example 2: Statement will remove 'b' item from the set.
```
set_1 = {'a', 'b', 'f', 'h', 'b', 'j'}
set_1.discard('b')
print(set_1)

Output: {'a', 'f', 'j', 'h'}
```
  Visit this page to understand difference between remove, discard and pop functions
Pop item from Set: pop() function will remove random item from the set. Pop function will throw error if set is empty.
```
Syntax: set_object.pop()
```
- Example 1: Statement will remove random item from the set
```
set_1 = {'a', 'b', 'f', 'h', 'j'}
set_1.pop()

Output: 'a'
```
- Example 2: Statement will fail since set is empty. Solution is to check if set is not empty before running pop function.
```
set_1 = set()
set_1.pop()

Output: KeyError: 'pop from an empty set'


Solution: Check length of set before running pop function
if len(set_1)>0:
	set_1.pop()
```
  Visit this page to understand difference between remove, discard and pop functions

Copy Set: copy() function returns a copy of the input set


Syntax: set_object.copy()

set_1 = {1, 2, 3, 6, 'A'}
set_2 = set_1.copy()
print(set_1)
Output 2: {1, 2, 3, 6, 'A'}


set_2.pop()   # Removing item from set_2
Output 3:  1


print(set_2)   # 'A' value not present in set_2
Output 4: {2, 3, 6, 'A'}


print(set_1)   # 'A' value is still present in set_1
Output 5: [{1, 2, 3, 6, 'A'}

Clear Set: clear() function remove all items from set.


Syntax: set_object.clear()

set_1 = {1, 2, 3, 6, 'A'}
set_1.clear()
print(set_1)

Output: set()

issubset: issubset() function will only return True if all the elements of first set is present in second sets.


Syntax : set_1.issubset(set_2)

Example 1: All elements of Set_2 are present in Set_1.


set_1 = {1,8,'T',5,2,3,6,'A'}
set_2 = {2, 3, 6, 'A'}

set_2.issubset(set_1)

Output: True

Example 2: All elements of Set_1 are not present in Set_2.


set_1 = {1,8,'T',5,2,3,6,'A'}
set_2 = {2, 3, 6, 'A'}

set_1.issubset(set_2)

Output: False

Example 3: Set_1 and Set_3 have only 1 common element.


set_2 = {2, 3, 6, 'A'}
set_3 = {6, 1, 's', 'i'}

set_2.issubset(set_3)

Output: False

Example 4: Set_2 and Set_4 have same items.


set_2 = {2, 3, 6, 'A'}
set_4 = {2, 3, 6, 'A'}

set_2.issubset(set_4)

Output: True

issuperset: issuperset() function will only return True if all the elements of second set is present in first sets.


Syntax : set_1.issuperset(set_2)

Example 1: All elements of Set_2 are present in Set_1.


set_1 = {1,8,'T',5,2,3,6,'A'}
set_2 = {2, 3, 6, 'A'}

set_1.issuperset(set_2)

Output: True

Example 2: All elements of Set_1 are not present in Set_2.


set_1 = {1,8,'T',5,2,3,6,'A'}
set_2 = {2, 3, 6, 'A'}

set_2.issuperset(set_1)

Output: False

Example 3: Set_1 and Set_3 have only 1 common element.


set_2 = {2, 3, 6, 'A'}
set_3 = {6, 1, 's', 'i'}

set_2.issuperset(set_3)

Output: False

Example 4: Set_2 and Set_4 have same items.


set_2 = {2, 3, 6, 'A'}
set_4 = {2, 3, 6, 'A'}

set_2.issuperset(set_4)

Output: True

union: union() function will combine elements of 2 sets and return as new set.


Syntax : set_1.union(set_2)

Example 1: Combining all the elements from 2 sets without duplicates


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_1.union(set_2)
print(set_4)

Output: {1, 2, 3, 'T', 6, 8, 'A'}

Example 2: Combining all the elements from 2 sets without duplicates


set_2 = {2, 3, 6, 'A'}
set_3 = {7, 1, 's', 'i'}

set_4 = set_2.union(set_3)
print(set_4)

Output: {1, 2, 3, 'i', 's', 6, 7, 'A'}

difference: difference() function will return all elements that are in one set but not in the other set as a new set.


Syntax : set_1.difference(set_2)

Example 1: Subtracting Set_1 from Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_1.difference(set_2)
print(set_4)

Output: {8, 1, 'T'}

Example 2: Subtracting Set_2 from Set_1


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_2.difference(set_1)
print(set_4)

Output: {2, 3, 6}

Example 3: Subtracting Set_2 from Set_3 with no common element


set_2 = {2, 3, 6, 'A'}
set_3 = {7, 1, 's', 'i'}

set_4 = set_2.difference(set_3)
print(set_4)

Output: {'A', 2, 3, 6}

difference_update: difference_update() function will update the 1st set and remove all the common elements present in other set.


Syntax : set_1.difference_update(set_2)

Example 1: Subtracting Set_1 from Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_1.difference_update(set_2)
print(set_1)

Output: {8, 1, 'T'}

Example 2: Subtracting Set_2 from Set_1


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_2.difference_update(set_1)
print(set_2)

Output: {2, 3, 6}

intersection: intersection() function will return all the common elements present in 2 sets as a new set.


Syntax : set_1.difference(set_2)

Example 1: Intersecting Set_1 and Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_1.intersection(set_2)
print(set_4)

Output: {'A'}

Example 2: Intersecting Set_2 and Set_1


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_2.intersection(set_1)
print(set_4)

Output: {'A'}

Example 3: Intersection will return empty Set since there is no common element


set_2 = {2, 3, 6, 'A'}
set_3 = {7, 1, 's', 'i'}

set_4 = set_2.intersection(set_3)
print(set_4)

Output: set()

intersection_update: intersection_update() function will update the 1st set with all the common elements present in both sets.


Syntax : set_1.difference_update(set_2)

Example 1: Intersecting Set_1 and Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_1.intersection_update(set_2)
print(set_1)

Output: {'A'}

Example 2: Intersecting Set_2 and Set_1


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_2.intersection_update(set_1)
print(set_2)

Output: {'A'}

isdisjoint: isdisjoint() function will return True if two sets have a null intersection(no common item).


Syntax : set_1.isdisjoint(set_2)

Example 1: Set_1 and Set_2 does not have any common element.


set_1 = {1,8,'T',5}
set_2 = {2, 3, 6, 'A'}

set_1.isdisjoint(set_2)

Output: True

Example 2: Set_2 and Set_3 have 1 common element.


set_2 = {2, 3, 6, 'A'}
set_3 = {6, 1, 's', 'i'}

set_2.isdisjoint(set_3)

Output: False

Example 3: Set_4 and Set_2 have same items.


set_2 = {2, 3, 6, 'A'}
set_4 = {2, 3, 6, 'A'}

set_2.isdisjoint(set_4)

Output: False

symmetric_difference: symmetric_difference() function will return all the non-common elements from both sets as a new set. This is opposite of intersection.


Syntax : set_1.symmetric_difference(set_2)

Example 1: Non common elements from Set_1 and Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_1.symmetric_difference(set_2)
print(set_4)

Output: {1, 2, 3, 'T', 6, 8}

Example 2: Non common elements from Set_1 and Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_4 = set_2.symmetric_difference(set_1)
print(set_4)

Output: {1, 2, 3, 'T', 6, 8}

Example 3: Non common elements from Set_3 and Set_2


set_2 = {2, 3, 6, 'A'}
set_3 = {7, 1, 's', 'i'}

set_4 = set_2.symmetric_difference(set_3)
print(set_4)

Output: {1, 'i', 's', 2, 3, 6, 7, 'A'}

symmetric_difference_update: symmetric_difference_update() function will update 1st set with all the non-common elements from both sets. This is opposite of intersection_update.


Syntax : set_1.symmetric_difference_update(set_2)

Example 1: Non common elements from Set_1 and Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_1.symmetric_difference_update(set_2)
print(set_1)

Output: {1, 2, 3, 'T', 6, 8}

Example 2: Non common elements from Set_1 and Set_2


set_1 = {1,8,'T','A'}
set_2 = {2, 3, 6, 'A'}

set_2.symmetric_difference_update(set_1)
print(set_2)

Output: {1, 2, 3, 'T', 6, 8}

Python Set Functions

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Python Set Functions