Set in Python

Python Sets

In Python, The Set is an unordered collection of data type that is iterable, mutable and has no duplicate elements. The order of elements in a set is undefined though it may consist of various elements.

The major advantage of using a set, as opposed to a list, is that it has a highly optimized method for checking whether a specific element is contained in the set.

Creating a Set

Sets can be created by using the built-in set() function with an iterable object or a sequence by placing the sequence inside curly braces, separated by ‘comma’, and it can not have mutable elements like list.

Lets create :

# Python program to demonstrate 

# Creation of Set in Python

  

# Creating a Set

set1 = set()

print("Intial blank Set: ")

print(set1)

  

# Creating a Set with 

# the use of a String

set1 = set("codedudle")

print("\nSet with the use of String: ")

print(set1)

  

# Creating a Set with

# the use of Constructor

# (Using object to Store String)

String = 'codedudle'

set1 = set(String)

print("\nSet with the use of an Object: " )

print(set1)

  

# Creating a Set with

# the use of a List

set1 = set(["code","dudle"])

print("\nSet with the use of List: ")

print(set1)




output :




Intial blank Set: 
set()

Set with the use of String: 
{'l', 'e', 'c', 'u', 'd', 'o'}

Set with the use of an Object: 
{'l', 'e', 'c', 'u', 'd', 'o'}

Set with the use of List: 
{'code', 'dudle'}




After creation of set it contains unique values, but at the time of set creation, multiple duplicate values can also be passed into it. Type of elements in a set need not be the same, heterogenous data type values can also be passed to the set.

# Creating a Set with 

# a List of Numbers

# (Having duplicate values)

set1 = set([1, 2, 8, 4, 3, 3, 3, 6, 5])

print("\nSet with the use of Numbers: ")

print(set1)

  

# Creating a Set with 

# a mixed type of values

# (Having numbers and strings)

set1 = set([1, 2, 'code', 4 , 6, 'dudle'])

print("\nSet with the use of Mixed Values")

print(set1)




output :




Set with the use of Numbers: 
{1, 2, 3, 4, 5, 6, 8}

Set with the use of Mixed Values
{1, 2, 4, 6, 'code', 'dudle'}




Adding Elements to a Set

Using add() method

We can add elements to the Set by using built-in add() function. Only one element at a time can be added to the set by using add() method, not more than that, we can add multiple eements by the help of loops at a time with the use of add() method.

Note – Lists cannot be added to a set as elements because Lists are not hashable whereas Tuples can be added because tuples are immutable and hence Hashable.




# Python program to demonstrate 

# Addition of elements in a Set

  

# Creating a Set

set1 = set()

print("Intial blank Set: ")

print(set1)

  

# Adding element and tuple to the Set

set1.add(2)

set1.add(5)

set1.add((7,4))

print("\nSet after Addition of Three elements: ")

print(set1)

  

# Adding elements to the Set

# using Iterator

for i in range(1, 8):

    set1.add(i)

print("\nSet after Addition of elements from 1-7: ")

print(set1)




output :




Intial blank Set: 
set()

Set after Addition of Three elements: 
{(7, 4), 2, 5}

Set after Addition of elements from 1-7: 
{1, 2, 3, 4, 5, 6, 7, (7, 4)}




Using update() method

For addition of two or more elements Update() method is used. The update() method accepts lists, strings, tuples as well as other sets as its arguments. In all of these cases, duplicate elements are avoided.

# Python program to demonstrate 

# Addition of elements in a Set

  

# Addition of elements to the Set

# using Update function

set1 = set([ 4, 5, (6, 7)])

set1.update([10, 11])

print("\nSet after Addition of elements using Update: ")

print(set1)




output :




Set after Addition of elements using Update: 
{4, 5, (6, 7), 10, 11}







Accessing a Set

Set items cannot be accessed by referring to an index like we have done tuple, the sets are unordered the items has no index. But you can loop through the set items using a for loop, or ask if a specified value is present in a set, by using the in keyword.




# Python program to demonstrate # Accessing of elements in a set    # Creating a set set1 = set(["code", "dudle"]) print("\nInitial set") print(set1)    # Accessing element using # for loop print("\nElements of set: ") for i in set1:     print(i, end=" ")    # Checking the element # using in keyword print("code" in set1) output : Initial set {'code', 'dudle'} Elements of set: code dudle True




Removing elements from the Set

By the help of remove() method or discard() method we can perform the operation.

Elements can be removed from the Set by using built-in remove() function but a KeyError arises if element doesn’t exist in the set. To remove elements from a set without KeyError, use discard(), if the element doesn’t exist in the set, it remains unchanged.

# Python program to demonstrate 

# Deletion of elements in a Set

  

# Creating a Set

set1 = set([1, 2, 3, 4, 5, 6, 

            7, 8, 9, 10, 11, 12])

print("Intial Set: ")

print(set1)

  

# Removing elements from Set

# using Remove() method

set1.remove(5)

set1.remove(6)

print("\nSet after Removal of two elements: ")

print(set1)

  

# Removing elements from Set

# using Discard() method

set1.discard(8)

set1.discard(9)

print("\nSet after Discarding two elements: ")

print(set1)

  

# Removing elements from Set

# using iterator method

for i in range(1, 5):

    set1.remove(i)

print("\nSet after Removing a range of elements: ")

print(set1)




output :




Intial Set: 
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}

Set after Removal of two elements: 
{1, 2, 3, 4, 7, 8, 9, 10, 11, 12}

Set after Discarding two elements: 
{1, 2, 3, 4, 7, 10, 11, 12}

Set after Removing a range of elements: 
{7, 10, 11, 12}




Using pop() method

pop() function can also be used to remove and return an element from the set, but it removes only the last element of the set.

Note – If the set is unordered then there’s no such way to determine which element is popped by using the pop() function.




# Python program to demonstrate 

# Deletion of elements in a Set

  

# Creating a Set

set1 = set([1, 2, 3, 4, 5, 6, 

            7, 8, 9, 10, 11, 12])

print("Intial Set: ")

print(set1)

  

# Removing element from the 

# Set using the pop() method

set1.pop()

print("\nSet after popping an element: ")

print(set1)







output :

Intial Set: 
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}

Set after popping an element: 
{2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}







Using clear() method

To remove all the elements from the set, clear() function is used.

#Creating a set

set1 = set([1,2,3,4,5])

print("\n Initial set: ")

print(set1)

  

  

# Removing all the elements from 

# Set using clear() method

set1.clear()

print("\nSet after clearing all the elements: ")

print(set1)




output :




Initial set:
{1, 2, 3, 4, 5}

Set after clearing all the elements: 
set()




Frozen sets in Python are immutable objects that only support methods and operators that produce a result without affecting the frozen set or sets to which they are applied. While elements of a set can be modified at any time, elements of the frozen set remain the same after creation.
If no parameters are passed, it returns an empty frozenset.




# Python program to demonstrate 

# working of a FrozenSet 

  

# Creating a Set

String = ('c', 'o', 'd', 'e', 'd', 'u', 'd', 'l','e')

  

Fset1 = frozenset(String)

print("The FrozenSet is: ")

print(Fset1)

  

# To print Empty Frozen Set

# No parameter is passed

print("\nEmpty FrozenSet: ")

print(frozenset())




output :




The FrozenSet is: 
frozenset({'l', 'e', 'c', 'u', 'd', 'o'})

Empty FrozenSet: 
frozenset()




In this article i have briefly explained the Sets in Python




Next article : Dictionary in Python







Recommended post : Introduction to Data types

String in Python

Tuple in Python
















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