Find size of a set in Python

This post will discuss how to find the size of a set in Python.

1. Using `len()` function

The Pythonic way to get the total number of elements in a set is using the built-in function len(). This function returns a non-negative value representing the number of items in an object that has a length attribute. Here is an example of how to use this function on a set:

s = {1, 2, 3}

n = len(s)

print(n) # 3

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If the set is empty, the len() function returns zero as expected.

s = set()

n = len(s)

print(n) # 0

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Note that a set in a boolean context is treated as False if empty and True otherwise. Therefore, we should avoid using the len() function in boolean contexts to check if a set is empty.

s = set()

if not s:

print('The set is empty')

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The len() function is implemented with __len__ function. Although not very Pythonic, the __len__ function can be called directly:

s = {1, 2, 3}

print(s.__len__()) # 3

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2. Using `collections.Counter()` class

Another way to find the size of a Python set is to use the collections.Counter() class from the collections module. We can create a Counter object from a set and then use its __len__() function to find the size of the set. Here is an example on how to use this function:

import collections

s = {1, 2, 3}

n = collections.Counter(s).__len__()

print(n) # 3

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However, it requires importing an external module and it may not be very efficient.

That’s all about finding the size of a set in Python.

Also See: Why len(x) is chosen over x.len()?

Find size of a set in Python

1. Using len() function

2. Using collections.Counter() class

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1. Using `len()` function

2. Using `collections.Counter()` class