# Sets

Unordered collection of items.

Every set element is

• Unique (no duplicates)
• Must be immutable

## Creating a Set

• Created by enclosing elements within {curly} brackets.
• Each item is separated by a comma.

#### Code

``````a = 2
set_a = {5, "Six", a, 8.2}
print(type(set_a))
print(set_a)``````

Output

<class ‘set’>
{8.2, 2, ‘Six’, 5}

Need not be in the same order as defined.

## No Duplicate Items

Sets contain unique elements

#### Code

``````set_a = {"a", "b", "c", "a"}
print(set_a)``````

Output

{‘b’, ‘a’, ‘c’}

## Immutable Items

Set items must be immutable. As List is mutable, Set cannot have list as an item.

#### Code

``````set_a = {"a", ["c", "a"]}
print(set_a)``````

Output

TypeError: unhashable type: ‘list’

## Creating Empty Set

We use

set() to create an empty set.

#### Code

``````set_a = set()
print(type(set_a))
print(set_a)``````

Output

<class ‘set’>
set()

## Converting to Set

set(sequence) takes any sequence as argument and converts to set, avoiding duplicates

### List to Set

#### Code

``````set_a = set([1,2,1])
print(type(set_a))
print(set_a)``````

Output

<class ‘set’>
{1, 2}

### String to Set

#### Code

``````set_a = set("apple")
print(set_a)``````

Output

{‘l’, ‘p’, ‘e’, ‘a’}

### Tuple to Set

#### Code

``````set_a = set((1, 2, 1))
print(set_a)``````

Output

{1, 2}

## Accessing Items

As sets are unordered, we cannot access or change an item of a set using

• Indexing
• Slicing

#### Code

``````set_a = {1, 2, 3}
print(set_a[1])
print(set_a[1:3])``````

Output

TypeError: ‘set’ object is not subscriptable

#### Code

``````set_a = {1, 3, 6, 2, 9}
print(set_a)``````

output

{1, 2, 3, 6, 7, 9}

set.update(sequence) adds multiple items to the set, and duplicates are avoided.

#### Code

``````set_a = {1, 3, 9}
set_a.update([2, 3])
print(set_a)``````

Output

{2, 1, 3, 9}

## Removing Specific Item

set.discard(value) takes a single value and removes if present.

#### Code

``````set_a = {1, 3, 9}
print(set_a)``````

Output

{1, 9}

set_a.remove(value) takes a value and remove if it present or raise an error.

#### Code

``````set_a = {1, 3, 9}
set_a.remove(5)
print(set_a)``````

Output

KeyError: 5

## Operations on Sets

You can perform the following operations on Sets

• clear()
• len()
• Iterating
• Membership Check

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