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

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 custom logic that will help perform various operations.

Syntax

len(set)

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, as 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 a set, 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 a time complexity of O(1). 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!