Frozen sets are unique data types in the Python programming language. They are similar to sets, with the main difference being that frozen sets are immutable. This means that once a frozen set is created, it cannot be changed or modified. In this article, we will dive into the basics of frozen sets, what makes them unique, and how to use them in your Python programs.

What are Frozen Sets in Python?

A frozen set is a data type in Python similar to a set. It is an unordered collection of unique elements, meaning that no aspect can appear more than once in the set. The main difference between a set and a frozen set is that frozen sets are immutable. This means that its elements cannot be changed, added, or removed once a frozen set is created.

Frozen Sets vs Sets

Frozen sets and sets have some similarities and differences. Both sets and frozen sets are unordered collections of unique elements. However, sets are mutable, while frozen sets are immutable. This means that you can add, remove, and change elements in a set but not in a frozen set. Additionally, sets are not hashable and cannot be used as keys in dictionaries, while frozen sets are hashable and can be used as keys.

How to Create Frozen Sets in Python

Creating a frozen set in Python is easy. To create a frozen set, use the frozenset() function, and pass in a collection of elements as the argument. For example:

				
					fruits = frozenset(["apple", "banana", "cherry"])
print(fruits)

Output:

				
					frozenset({'banana', 'cherry', 'apple'})

How to Use Frozen Sets in Python

Just like sets, frozen sets can be used for many different tasks in your Python programs. For example, you can use them to perform set operations like union, intersection, and difference.

Here’s an example of how you can perform a union operation between two frozen sets:

				
					fruits1 = frozenset(["apple", "banana", "cherry"])
fruits2 = frozenset(["mango", "banana", "orange"])
fruits_union = fruits1 | fruits2
print(fruits_union)

Output:

				
					frozenset({'banana', 'orange', 'cherry', 'mango', 'apple'})

Frozen Set Conversions in Python

In Python, other types can be converted into frozen sets.

1. Frozen set to set

You can use the set() constructor to convert a frozen set to a set.

				
					frozenset_obj = frozenset([1, 2, 3, 4])
set_obj = set(frozenset_obj)

There are several ways to convert between different data types in Python, including conversions between a frozen set and other data types:

2. From a list to a frozen set

Use the frozenset() function to convert a list to a frozen set. 

				
					>>> my_list = [1, 2, 3]
>>> my_frozen_set = frozenset(my_list)
>>> type(my_frozen_set)
<class 'frozenset'>

3. From a tuple to a frozen

Use the frozenset() function to convert a tuple to a frozen set.

				
					>>> my_tuple = (1, 2, 3)
>>> my_frozen_set = frozenset(my_tuple)
>>> type(my_frozen_set)
<class 'frozenset'>

4. From a frozen set to a set

Use the set() function to convert a frozen set to a set

				
					>>> my_frozen_set = frozenset([1, 2, 3])
>>> my_set = set(my_frozen_set)
>>> type(my_set)
<class 'set'>

5. From a frozen set to a list

Use the list() function to convert a frozen set to a list.

				
					>>> my_frozen_set = frozenset([1, 2, 3])
>>> my_list = list(my_frozen_set)
>>> type(my_list)
<class 'list'>

6. From a frozen set to a tuple

Use the tuple() function to convert a frozen set to a tuple.

				
					>>> my_frozen_set = frozenset([1, 2, 3])
>>> my_tuple = tuple(my_frozen_set)
>>> type(my_tuple)
<class 'tuple'>

Why Use Frozen Sets in Python?

Frozen sets have several unique use cases in Python. Here are a few of the main reasons why you might choose to use a frozen set:

  • As keys in dictionaries: Frozen sets can be used as keys because they are hashable and immutable.
  • As elements in sets: Frozen sets can be used as elements in sets because sets are mutable and can therefore contain mutable and immutable elements.
  • To ensure immutability: If you have a collection of elements that you do not want to change, you can use a frozen set to remain unchanged.

Limitations of Frozen Sets in Python

Although frozen sets have many useful use cases in Python, there are a few limitations to keep in mind. For example, frozen sets cannot be changed once they are created, which can make them less flexible than sets in certain situations. Additionally, because frozen sets are hashable, they cannot contain mutable elements like lists or dictionaries.

Wrap up

Frozen sets are an essential feature of the Python programming language. They are immutable sets that can be used in various situations, including as keys in dictionaries, set operations, and mathematical operations. Understanding frozen sets and their uses are essential for any Python programmer.


Thanks for reading. Happy coding!