Python set() Function — A Simple Guide with Video

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Python’s built-in set() function creates and returns a new set object. A set is an unordered collection of unique elements. Without an argument, set() returns an empty set. With the optional argument, set(iter) initializes the new set with the elements in the iterable.

Read more about sets in our full tutorial about Python Sets.

Python set() Function - Examples and Explanation


Learn by example! Here are some examples of how to use the set() built-in function:

You can create an empty set by skipping the argument:

>>> set()

If you pass an iterable—such as another list, a tuple, a set, or a dictionary—you obtain a new set object with elements obtained from the iterable:

>>> set([1, 2, 3])
{1, 2, 3}

Note that it really creates a new set object that is different from the one passed as an argument:

>>> x = {1, 2, 3}
>>> y = set(x)
>>> x is y
>>> x == y

The new set y has the same elements as the original set x. But it’s still a different object as you can see from the check x is y that returns False.

Video set()

Python set() Function โ€” A Simple Guide

Syntax set()

You can use the set() method with or without the optional iterable argument.

Syntax: There are two ways of using the constructor:
set() -> new empty set
set(iterable) -> new set initialized with elements in iterable

Interactive Shell Exercise: Understanding set()

Consider the following interactive code:

Exercise: Guess the output before running the code.

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Python’s built-in set() function creates and returns a new set object.

  • When used without an argument, it returns an empty set.
  • When used with the optional iterable argument, it initializes the new set with the elements in the iterable.
>>> set()
>>> set([1, 2, 3])
{1, 2, 3}

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