How to Create a Set in Python: Syntax and Examples

In Python, you create a set using the set() function or by enclosing items in curly braces {}. Sets store unique items without order, so duplicates are removed automatically.

Syntax

You can create a set in two main ways:

• Using curly braces: Enclose comma-separated values inside {}. Example: {1, 2, 3}
• Using the set() function: Pass an iterable like a list or string to set(). Example: set([1, 2, 3])

Note: To create an empty set, use set() because {} creates an empty dictionary.

python

my_set = {1, 2, 3}
my_other_set = set([4, 5, 6])
empty_set = set()

Example

This example shows how to create sets using both curly braces and the set() function. It also demonstrates that duplicates are removed automatically.

python

fruits = {'apple', 'banana', 'apple', 'orange'}
print(fruits)  # Duplicates removed

numbers = set([1, 2, 2, 3, 4])
print(numbers)  # Duplicates removed

empty = set()
print(empty)  # Empty set

Output

{'banana', 'orange', 'apple'}
{1, 2, 3, 4}
set()

Common Pitfalls

One common mistake is trying to create an empty set using {}, but this actually creates an empty dictionary. Always use set() for an empty set.

Another pitfall is expecting sets to keep the order of items. Sets do not keep order, so the output order may differ from the input.

python

empty_wrong = {}
print(type(empty_wrong))  # Outputs: <class 'dict'>

empty_right = set()
print(type(empty_right))  # Outputs: <class 'set'>

Output

<class 'dict'>
<class 'set'>

Quick Reference

Action	Syntax	Description
Create set with items	{1, 2, 3}	Set with unique items
Create set from list	set([1, 2, 3])	Convert list to set
Create empty set	set()	Empty set
Create empty dictionary	{}	Empty dictionary, not a set

Key Takeaways

Use curly braces {} or set() to create sets in Python.

Always use set() to create an empty set, not {}.

Sets automatically remove duplicate items and do not keep order.

Passing a list or other iterable to set() converts it to a set.

Remember that {} creates an empty dictionary, not a set.