freeCodeCamp/guide/english/python/learn-about-python-sets/index.md

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Learn About Python Sets

Sets in Python are a type of mutable but unordered data structure, which can only contain unique elements.

Creation:

set literal:

Curly brackets, {}, cannot be used to create an empty set:

>>> not_set = {}     # set constructor must be used to make empty sets.
>>> type(not_set)    # Empty curly brackets create empty dictionaries.
<class 'dict'>

You can only create an empty set by using the set() method.

>>> example_set = set()
>>> type(example_set)
<class 'set'>

However, if elements are included within the curly brackets, then it would be acceptable syntax to create a set.

>>> example_set_2 = {1, 2, 3}
>>> type(example_set_2)
<class 'set'>