## Tamilnadu Samacheer Kalvi 12th Computer Science Notes Chapter 9 Lists, Tuples, Sets and Dictionary Notes

**Four collections of data types in python programming language:**

Python programming language has four collections of data types such as List, Tuples, Set and Dictionary.

**List in Python:**

- A list in Python is known as a “sequence data type” like strings.
- It is an ordered collection of values enclosed within square brackets [ ].
- Each value of a list is called as element. It can be of any type such as numbers, characters, strings and even the nested lists as well.
- Values in a list can be changed

Tuple:

- Tuple consists of a number of values separated by comma and enclosed within parentheses even defined without parenthesis
- Values in a tuple cannot be changed.

“Singleton” Tuple:

Creating a Tuple with one element is called “Singleton” tuple.

**Set:**

- A set is created by placing all the elements separated by comma within a pair of curly brackets.
- The set() function can also used to create sets in Python.

**Set operations:**

- The python supports the set operations such as
- Union, Intersection, difference and Symmetric difference.

**Union:**

- Union includes all elements from two or more sets.
- In python, the operator | (pipe line) is used to union of two sets.
- The function union() is also used to join two sets in python.

Example:

Program to Join (Union) two sets using union operator and union function

set_A={2,4,6,8} set_B={‘A’, ‘B’, ‘C’, ‘D’}

U_set=set_A | set_B

print(U _set)

set_ U=set_ A.union(set_ B)

**Output:**

{2, 4, 6, 8, ‘A’, ‘D’, ‘C’, ‘B’}

{‘D’, 2, 4, 6, 8, ‘B’,’C’,’A’}

**Intersection:**

- Intersection includes the common elements in two sets.
- The operator & is used to intersect two sets in python.
- The function intersection() is also used to intersect two sets in python.

**Example:**

Program to insect two sets using intersection operator and intersection function

set_A={/A/, 2, 4, ‘D’}

set_B={‘A’, ‘B’, ‘C, ‘D’}

print(set_A&set_B)

print( set_A.intersection( set_B)

**output:**

{‘A’,’D’}

{‘A’, ‘D’}

Difference:

- Difference includes all elements that are in first set (say set A) but not in the second set (say set B).
- The minus (-) operator is used to difference set operation in python.
- The function difference() is also used to difference operation.

**Example:**

Program to difference of two sets using minus operator and difference function set_A={/A’/ 2,4, ‘D’} setJB={‘A’, ‘B’, ‘C, ‘D’} print(set_A – set B) print(set_A.difference( set_B))

**Output:**

{2,4}

{2,4}

**Symmetric difference:**

- Symmetric difference includes all the elements that are in two sets (say sets A and B) but not the one that are common to two sets.
- The caret (^) operator is used to symmetric difference set operation in python.
- The function symmetric_difference( ) is also used to do the same operation.

**Example:**

Program to symmetric difference of two sets using caret operator and symmetric difference function

set_A={‘A’, 2,4, ‘D’} set_B={/A// ‘B’, ‘C, ‘D’}

print(set_A A set_B)

print( set_A.symmetric_difference(set_B))

**Output:**

{2,4,’B’,’C’}

{2,4,’B’,’C’}

**Dictionary:**

- Dictionary is a mixed collection of elements.
- Unlike other collection data types such as a list or tuple, the dictionary type stores a key along with its element.
- The keys in a Python dictionary is separated by a colon (:) while the commas work as a separator for the elements.
- The key value pairs are enclosed with curly braces {}.

**Function :copy ()**

Description : Returns a copy of the list Syntax : List.copy()

**Function :count ()**

Description : Returns the number of similar elements present in the last.

Syntax : List.count(value)

**Function index ()**

Description : Returns the index value of the first recurring element

Syntax : List, index (element)

**Function : reverse ()**

Description: Reverses the order of the element in the list.

Syntax : List.reverse()

**Function: sort ()**

Description : Sorts the element in list Syntax : List.sort(reverse=True | False, key=myFunc)