Python | which is hashable and can be used as a dictionary key

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frozenset()

In Python, a set is a collection of unique elements, and it can be modified by adding or removing elements. However, sometimes you may want to create a set that cannot be modified. This is where the "frozenset()" function comes into play. In this article, we will discuss the frozenset() function, its usage, and provide examples to illustrate its use.

The frozenset() function is a built-in function in Python that creates an immutable set, i.e., a set that cannot be modified. Once a frozenset is created, it cannot be modified. The syntax of the function is as follows:

frozen_set = frozenset(iterable)

The "iterable" argument is a collection of elements that will be used to create the frozenset. The elements in the frozenset must be hashable, i.e., they must be able to be hashed so that they can be added to the set.

Let's take a look at some examples to illustrate the usage of the frozenset() function.

Example 1: Creating a Frozenset

my_set = {1, 2, 3, 4, 5}

frozen_set = frozenset(my_set)

print(frozen_set)

In this example, we have a set "my_set" with five elements. We then create a frozenset "frozen_set" using the frozenset() function. The output of this code will be:

frozenset({1, 2, 3, 4, 5})

Example 2: Using Frozenset as a Key in a Dictionary

frozen_set = frozenset(['a', 'b', 'c'])

my_dict = {frozen_set: 100}

print(my_dict[frozen_set])

In this example, we create a frozenset "frozen_set" from a list of elements. We then use the frozenset as a key in a dictionary "my_dict". Since the frozenset is immutable, it can be used as a key in a dictionary. The output of this code will be:

100

Example 3: Frozenset Operations

set1 = {1, 2, 3}

set2 = {3, 4, 5}

frozen_set1 = frozenset(set1)

frozen_set2 = frozenset(set2)

union_set = frozen_set1.union(frozen_set2)

intersection_set = frozen_set1.intersection(frozen_set2)

print(union_set)

print(intersection_set)

In this example, we have two sets "set1" and "set2". We then create frozensets "frozen_set1" and "frozen_set2" from these sets. We then perform set operations on the frozensets. The output of this code will be:

frozenset({1, 2, 3, 4, 5})

frozenset({3})

In conclusion, the frozenset() function is a useful tool in Python for creating immutable sets. It can be used to create keys in dictionaries or to perform set operations on immutable sets. By using the frozenset() function, you can ensure that a set is not modified and maintain data integrity in your Python code.