Frozen set behavior in Python

Introduction

A frozen set is like a regular set but cannot be changed after it is made. It helps keep data safe from accidental changes.

When you want a group of unique items that should not change.

When you need to use a set as a key in a dictionary.

When you want to share a set of items without risk of someone changing it.

When you want to make sure your data stays the same throughout the program.

Syntax

Python

frozenset(iterable)

The iterable can be a list, tuple, or another set.

Once created, you cannot add or remove items from a frozen set.

Examples

Create a frozen set from a list of numbers.

Python

fs = frozenset([1, 2, 3])

Create a frozen set from a set of strings.

Python

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

Create an empty frozen set.

Python

fs = frozenset()

Sample Program

This program creates a frozen set from a list with repeated numbers. It prints the frozen set and then tries to add a new item, which causes an error because frozen sets cannot be changed.

Python

fs = frozenset([1, 2, 3, 2])
print(fs)

# Trying to add an item will cause an error
try:
    fs.add(4)
except AttributeError as e:
    print('Error:', e)

Important Notes

Frozen sets are immutable, meaning they cannot be changed after creation.

You can use frozen sets as keys in dictionaries because they are hashable.

Frozen sets support operations like union, intersection, and difference, just like regular sets.

Summary

Frozen sets are sets that cannot be changed after they are created.

They are useful when you want to protect data from being modified.

You create them using the frozenset() function with an iterable.