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Key-Value Pairs

  • This lesson explains how dictionaries store data in key-value format in Python.

  • What is a Dictionary?

    A dictionary in Python is a data type used to store data in key–value pairs.

    • Each key is like a label

    • Each value is the data related to that key

    Think like a real dictionary:
    Word (Key) → Meaning (Value)

    Syntax to Create a Dictionary

    dictionary_name = {

        key1: value1,

        key2: value2,

        key3: value3

    }

    Rules of Dictionary

    • Keys must be unique

    • Keys are usually strings, numbers, or tuples

    • Values can be any data type

    • Dictionaries are written using curly braces { }

Student Dictionary

Stores student information using key–value pairs. 

student = {
    "name": "Amit",
    "age": 20,
    "course": "Python"
}

print(student)

Product Details Dictionary

This dictionary stores product details like name, price, and stock. 

product = {
    "product_name": "Laptop",
    "price": 45000,
    "stock": 10
}
print(product)

Dictionary with Different Data Types

Shows that dictionary values can be of different types. 

data = {
    "name": "Riya",
    "marks": 85,
    "passed": True,
    "subjects": ["Math", "Science"]
}

print(data)

Empty Dictionary

Creates an empty dictionary to add data later. 

my_dict = {}
print(my_dict)

Dictionary Using dict() Function

Creates a dictionary using the built-in dict() function. 

student = dict(name="Rahul", age=21, city="Delhi")
print(student)

  • What is Dictionary Constructor?

    A dictionary constructor is another way to create a dictionary using the built-in dict() function instead of { }.

    It is useful when:

    • Creating dictionaries in a clean format

    • Converting other data types into a dictionary

    • Passing key-value pairs as arguments

    Syntax of Dictionary Constructor

    dict(key1=value1, key2=value2, key3=value3)

Basic Dictionary Constructor

Creates a dictionary using dict() with key-value arguments. 

student = dict(name="Amit", age=20, course="Python")
print(student)

Dictionary from List of Tuples

Creates a dictionary by converting a list of key-value tuples. 

data = [("name", "Riya"), ("marks", 85), ("grade", "A")]
student = dict(data)
print(student)

Dictionary from Two Lists

Creates a dictionary by combining two lists using zip(). 

keys = ["name", "age", "city"]
values = ["Rahul", 22, "Mumbai"]

person = dict(zip(keys, values))
print(person)
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