Python Set: How to create an empty set and declare a set

A Python set is a set of items written with curly braces.

s = {'a', 'b'}

Empty set

Both set and dictionary use curly braces and only curly braces represent a dictionary with no element.

s = {}

print(type(s))  # <class 'dict'>

An empty set is declared by set(), a Python built-in function, as follows.

s = set()

print(s)  # set()
print(type(s))  # <class 'set'>

How to use set()

s = set(3)
# TypeError: 'int' object is not iterable

It can't take values, but iterables (set, list, tuple, etc).

s1 = set({1, 2, 3})
s2 = set([4, 5, 6, 6])
s3 = set((7, 7, 7))

print(s1)  # {1, 2, 3}
print(s2)  # {4, 5, 6}
print(s3)  # {7}

Python Set

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