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Sets in Python

Answer»

Initializing Sets:

Sets are initialized using curly braces {} or set() in python.

A python set is basically an unordered collection of unique values, i.e. it will automatically remove duplicate values from the set.

s = {1, 2, 3}
print(s)
s = set([1, 2, 3])
print(s)
s = {1, 2, 3, 3, 2, 4, 5, 5}
print(s)
Output:
{1, 2, 3}
{1, 2, 3}
{1, 2, 3, 4, 5}

Inserting elements in set:

We can insert a single element into a set using the add function of sets.

s = {1, 2, 3, 3, 2, 4, 5, 5}
print(s)
# Insert single element
s.add(6)
print(s)
Output:
{1, 2, 3, 4, 5}
{1, 2, 3, 4, 5, 6}

To insert multiple elements into a set, we use the update function and pass a list of elements to be inserted as parameters.

s = {1, 2, 3, 3, 2, 4, 5, 5}
# Insert multiple elements
s.update([6, 7, 8])
print(s)
Output:
{1, 2, 3, 4, 5, 6, 7, 8}

Deleting elements from the set:

We can delete elements from a set using either the remove() or the discard() function.

s = {1, 2, 3, 3, 2, 4, 5, 5}
print(s)
# Remove will raise an error if the element is not in the set
s.remove(4)
print(s)
# Discard doesn't raise any errors
s.discard(1)
print(s)
Output:
{1, 2, 3, 4, 5}
{1, 2, 3, 5}
{2, 3, 5}

Operators in sets:

The below table shows the operators used for sets:

OperatorsWhat it does
| (Union)Returns all the unique elements in both the sets.
& (Intersection)Returns all the elements common to both the sets.
- (Difference)Returns the elements that are unique to the first set
^(Symmetric Difference)Returns all the elements not common to both the sets.

The set operators are represented in the Venn Diagram below:

Examples:

a = {1, 2, 3, 3, 2, 4, 5, 5}
b = {4, 6, 7, 9, 3}
# Performs the Intersection of 2 sets and prints them
print(a & b)
# Performs the Union of 2 sets and prints them
print(a | b)
# Performs the Difference of 2 sets and prints them
print(a - b) 
# Performs the Symmetric Difference of 2 sets and prints them
print(a ^ b)
Output:
{3, 4}
{1, 2, 3, 4, 5, 6, 7, 9}
{1, 2, 5}
{1, 2, 5, 6, 7, 9}


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