Learn About Python Sets


title: Learn About Python Sets

Sets in Python are a type of mutable but unordered data structure, which can only contain unique elements. In other words, it is equivalent to sets in math.

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'>

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Converting Iterable to Set

If set(...) contains an iterable such as a list, a string, or a tuple as an element, it will return a set containing its’ elements. This will remove all duplicate values from the list.

>>> example_set_3 = set('some string') >>> example_set_3 {' ', 't', 'g', 'o', 'r', 'i', 's', 'e', 'n', 'm'}

If you want to convert an iterable like a list to a set, you can do that by passing it to the set() function.

>>> a = [11,2,2,6,6,4,8,9,9,7] >>> a = set(a) >>> print(a) # {2, 4, 6, 7, 8, 9, 11}

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