Python FrozenSet

The frozenset() is an inbuilt function is Python which takes an iterable object as input and makes them immutable. Simply it freezes the iterable objects and makes them unchangeable.

In Python, frozenset is same as set except its elements are immutable. This function takes input as any iterable object and converts them into immutable object. The order of element is not guaranteed to be preserved.

Example #1:

If no parameters are passed to frozenset() function then it returns a empty frozenset type object.

# Python program to understand frozenset() function 
  
# tuple of numbers 
nu = (1, 2, 3, 4, 5, 6, 7, 8, 9) 
  
# converting tuple to frozenset 
fnum = frozenset(nu) 
  
# printing details 
print("frozenset Object is : ", fnum) 

Output:

frozenset Object is : frozenset({1, 2, 3, 4, 5, 6, 7, 8, 9})

Example #2: Uses of frozenset().

Since frozenset object are immutable they are mainly used as key in dictionary or elements of other sets. Below example explains it cle

  # creating a dictionary  
Student = {"name": "Ankit", "age": 21, "sex": "Male",  
           "college": "MNNIT Allahabad", "address": "Allahabad"} 
  
# making keys of dictionary as frozenset 
key = frozenset(Student) 
  
# printing keys details 
print('The frozen set is:', key) 

Output:

The frozen set is: frozenset({'college', 'address', 'sex', 'age', 'name'})

Example #3: Warning

If by mistake we want to change the frozenset object then it throws an error “‘frozenset’ object does not support item assignment“.

# Python program to understand 
# use of frozenset function 
  
# creating a list  
favourite_subject = ["OS", "DBMS", "Algo"] 
  
# making it frozenset type 
f_subject = frozenset(favourite_subject) 
  
# below line will generate error 
  
f_subject[1] = "Networking"

Output:

Traceback (most recent call last): File "/home/0fbd773df8aa631590ed0f3f865c1437.py", line 12, in f_subject[1] = "Networking" TypeError: 'frozenset' object does not support item assignment

Example 4-

Set & Frozenset keeps only the unique values

a = frozenset((1,2,3,3))
b = (1,2,3,3)
print(a, b) # {1, 2, 3} / (1, 2, 3, 3)