Notes
Introduction to Python
Python Installation Using Python Install Manager (Windows)
Running Python Programs (Interactive Mode & Script Mode)
Python Tokens (Keywords, Identifiers, Literals, Operators)
Printing in Python
Variables and Data Types in Python
Type Casting in Python
Data Types in Python
Input Function in Python
Operators in Python
Arithmetic Operators in Python
Comparison Operators in Python
Logical Operators in Python
Membership and Identity Operators in Python
Assignment Operators in Python
Bitwise Operators in Python
Operator Precedence in Python
Conditional Statements in Python
Nested `if-else` in Python
`eval()` Function in Python
`for` Loop in Python
`dir()` Function in Python
`while` Loop in Python
`breakpoint()` Function in Python
`break` and `continue` in Python
`locals()` Function in Python
Tuple in Python
Abstraction in Python
`globals()` Function in Python
Set in Python
`enumerate()` Function in Python
Dictionary in Python
`sorted()` Function in Python
`reversed()` Function in Python
`zip()` Function in Python
`map()` Function in Python
`filter()` Function in Python
`next()` Function in Python
`iter()` Function in Python
`sum()` Function in Python
`min()` Function in Python
`max()` Function in Python
`all()` Function in Python
`any()` Function in Python
`abs()` Function in Python
`round()` Function in Python
`pow()` Function in Python
`divmod()` Function in Python
`bin()` Function in Python
`oct()` Function in Python
`hex()` Function in Python
`chr()` Function in Python
Polymorphism in Python
Inheritance in Python
`ord()` Function in Python
Class Method in Python
Class in Python
Object in Python
Static Method in Python
Characteristics of Object-Oriented Programming (OOP)
Encapsulation in Python
List in Python
String in Python
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Dictionary in Python [ English ]

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1. Introduction

A dictionary in Python is a collection of key-value pairs. It is used to store data in a structured form where each value is associated with a unique key.

2. Characteristics of Dictionary

3. Creating a Dictionary

Syntax

dict_name = {key1: value1, key2: value2}

Example

student = {
    "name": "Rahul",
    "age": 20,
    "marks": 85
}

Empty Dictionary

d = {}

4. Accessing Values

Using Key

student = {"name": "Rahul", "age": 20}

print(student["name"])

Output

Rahul

Using get() Method

print(student.get("age"))

5. Adding and Updating Elements

student = {"name": "Rahul"}

student["age"] = 20      # add
student["name"] = "Amit" # update

print(student)

6. Removing Elements

Using pop()

student.pop("age")

Using del

del student["name"]

Using clear()

student.clear()

7. Dictionary Methods

Method Description
keys() Returns all keys
values() Returns all values
items() Returns key-value pairs
update() Updates dictionary
pop() Removes element
clear() Removes all elements

8. Looping Through Dictionary

student = {"name": "Rahul", "age": 20}

for key in student:
    print(key, student[key])

9. Nested Dictionary

students = {
    "s1": {"name": "Rahul", "age": 20},
    "s2": {"name": "Amit", "age": 22}
}

print(students["s1"]["name"])

Output

Rahul

10. Membership Operators

print("name" in student)
print("marks" not in student)

11. Important Points

12. Difference Between List and Dictionary

Feature List Dictionary
Access Index Key
Structure Ordered Key-value
Syntax [ ] { }

13. Practical Example

student = {
    "name": "Rahul",
    "marks": 80
}

student["marks"] += 10

print(student)

14. Summary

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