Python Program to Add a Key-Value Pair to a Dictionary

Introduction

Adding a key-value pair to a dictionary is a common task in Python programming. A dictionary is a mutable data structure, meaning that you can modify it by adding or removing key-value pairs as needed. This tutorial will guide you through creating a Python program that adds a new key-value pair to an existing dictionary.

Example:

• Input Dictionary: {'name': 'John', 'age': 25}
• Key to Add: 'city'
• Value to Add: 'New York'
• Output Dictionary: {'name': 'John', 'age': 25, 'city': 'New York'}

Problem Statement

Create a Python program that:

• Takes an existing dictionary.
• Adds a new key-value pair to the dictionary.
• Displays the updated dictionary.

Solution Steps

1. Create a Dictionary: Initialize a dictionary with some key-value pairs.
2. Add a New Key-Value Pair: Use the assignment operation to add a new key-value pair to the dictionary.
3. Display the Updated Dictionary: Use the print() function to display the updated dictionary.

Python Program

# Python Program to Add a Key-Value Pair to a Dictionary
# Author: https://www.rameshfadatare.com/

# Step 1: Create a dictionary with key-value pairs
my_dict = {
    'name': 'John',
    'age': 25
}

# Step 2: Take key and value input from the user
new_key = input("Enter the key to add: ")
new_value = input("Enter the value for the key: ")

# Step 3: Add the new key-value pair to the dictionary
my_dict[new_key] = new_value

# Step 4: Display the updated dictionary
print("The updated dictionary is:", my_dict)

Explanation

Step 1: Create a Dictionary with Key-Value Pairs

• A dictionary my_dict is created with some initial key-value pairs, such as 'name': 'John' and 'age': 25.

Step 2: Take Key and Value Input from the User

• The input() function prompts the user to enter a new key and value. These inputs are stored in the variables new_key and new_value, respectively.

Step 3: Add the New Key-Value Pair to the Dictionary

• The new key-value pair is added to the dictionary using the assignment operation my_dict[new_key] = new_value. This creates a new entry in the dictionary or updates the value if the key already exists.

Step 4: Display the Updated Dictionary

• The print() function is used to display the dictionary after the new key-value pair has been added.

Output Example

Example 1:

Enter the key to add: city
Enter the value for the key: New York
The updated dictionary is: {'name': 'John', 'age': 25, 'city': 'New York'}

Example 2:

Enter the key to add: country
Enter the value for the key: USA
The updated dictionary is: {'name': 'John', 'age': 25, 'country': 'USA'}

Example 3:

Enter the key to add: profession
Enter the value for the key: Engineer
The updated dictionary is: {'name': 'John', 'age': 25, 'profession': 'Engineer'}

Conclusion

This Python program demonstrates how to add a new key-value pair to an existing dictionary. Understanding how to modify dictionaries is essential for efficiently managing and updating data in Python programs. The ability to dynamically add or update key-value pairs is particularly useful in scenarios where data is continuously changing or being expanded.