The length of the Set means the number of elements in the Set, which is the size of that specific object. Based on the length, you can create a custom logic that will be helpful to perform many operations.

To get the length of a Set in Python, you can use the len() function.

Syntax

len(set)

Visual Representation

Example

# Define a set
new_set = {2, 4, 6, 8}

# Get the length of the set
print(len(new_set))

# 4

The above Set contains four elements.

Empty Set

What if the Set is empty? If you pass that, what will be the output. Let’s find out.

# Define a set
empty_set = set()

# Get the length of the set
print(len(empty_set))

# 0

If a Set has no elements, meaning it has 0 elements.

Handling Duplicates

The len() is a basic function that returns the count of distinct elements since a Set automatically removes duplicates.

# Define a set
main_set = {11, 21, 21, 19, 19, 11}

# Get the length of the set
print(len(main_set))

# 3

We got the length three because Set can’t allow duplicate elements. Only elements 11, 21, and 19 are unique, and the length() only reflects unique elements.

Nested Set

You cannot create a nested Set because Sets are not hashable, and that’s why it cannot be an element of a Set. And that’s why you cannot use the len() function on a nested Set because it does not exist.

Set of tuples

If you are working with a Set of tuples and some of them are duplicates, it will remove the duplicate tuples and return the count of unique tuples.

# Define a set of tuples
main_set = {(11, 21), (21, 19), (21, 19)}

# Get the length of the set
print(len(main_set))

# 2

Counting unique words

If you have a large string and you want to find unique words in that sentence, you can use the len(set). But how, let’s find out.

text = "What is Python? How to learn Python? Why Python is popular?"

words = text.split()

unique_words = set(words)

print(unique_words)

# Output: {'popular?', 'What', 'learn', 'to', 'Python?', 'is', 'How', 'Python', 'Why'}

print(f"Unique words: {len(unique_words)}")

# Output: Unique words: 9

Frozen Sets

You can use fronzenset, which behaves like Sets, but you cannot modify it after creation. The len() function also returns the number of elements of the frozenset.

frozen = frozenset([11, 21, 31])

print(len(frozen))  # Output: 3

# frozen.add(4)     # Raises AttributeError

Performance and Efficiency

The len() function has O(1) time complexity. Even if the Set is large, it is still efficient.

import random

# Deduplicate a list of 1 million elements
big_list = [random.randint(1, 100) for _ in range(1_000_000)]

unique_count = len(set(big_list))

print(unique_count)
# Output: 100

That’s all!