Python Dictionaries

A Dictionary is a collection used to store data in key-value pairs. Dictionaries are ordered, changeable, and do not allow duplicate keys.

Creating a Dictionary

student = {
    "name": "John",
    "age": 20,
    "city": "Delhi"
}

print(student)

Output:

{'name': 'John', 'age': 20, 'city': 'Delhi'}

Access Dictionary Items

You can access values using their keys.

Syntax

dictionary_name[key]

Example

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

print(student["name"])

Output:

John

Using get()

The get() method returns the value of a specified key.

Syntax

dictionary_name.get(key)

Example

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

print(student.get("age"))

Output:

20

Get All Keys

The keys() method returns all dictionary keys.

Example

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

print(student.keys())

Output:

dict_keys(['name', 'age'])

Get All Values

The values() method returns all dictionary values.

Example

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

print(student.values())

Output:

dict_values(['John', 20])

Get Key-Value Pairs

The items() method returns all key-value pairs.

Example

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

print(student.items())

Output:

dict_items([('name', 'John'), ('age', 20)])

Check if Key Exists

Example

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

if "name" in student:
    print("Key exists")

Output:

Key exists

Dictionary Length

Example

student = {
    "name": "John",
    "age": 20,
    "city": "Delhi"
}

print(len(student))

Output:

3

Loop Through a Dictionary

Example

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

for key, value in student.items():
    print(key, value)

Output:

name John
age 20

Summary

• Dictionaries store data in key-value pairs.
• Keys must be unique.
• Values can be of any data type.
• Use [] or get() to access values.
• keys(), values(), and items() are commonly used dictionary methods.
• Dictionaries are mutable, so they can be modified after creation.