Database of Contacts using File Storage - Python Programming Exercise

import os
import pickle

# Class to represent a Contact with name, phone, and email
class Contact:
    def __init__(self, name, phone, email):
        self.name = name  # Contact's name
        self.phone = phone  # Contact's phone number
        self.email = email  # Contact's email address

    # String representation of a contact
    def __str__(self):
        return f"Name: {self.name}, Phone: {self.phone}, Email: {self.email}"

# Class to manage the database of contacts
class ContactsDatabase:
    def __init__(self, file_name):
        self.file_name = file_name  # File name to load/save contacts
        self.contacts = []  # List to store contacts
        self.load_from_file()  # Load existing contacts from file (if any)

    # Method to add a new contact
    def add_contact(self, name, phone, email):
        new_contact = Contact(name, phone, email)  # Create a new Contact object
        self.contacts.append(new_contact)  # Add the contact to the list
        print(f"Contact {name} added.")  # Notify that the contact has been added

    # Method to list all contacts in the database
    def list_contacts(self):
        if not self.contacts:  # Check if there are no contacts
            print("No contacts available.")  # Inform the user that there are no contacts
        else:
            for contact in self.contacts:  # Loop through the list of contacts
                print(contact)  # Print each contact's details

    # Method to save the contacts list to a file
    def save_to_file(self):
        try:
            with open(self.file_name, 'wb') as file:  # Open the file in write-binary mode
                pickle.dump(self.contacts, file)  # Serialize and save the contacts list to the file
            print("Contacts saved successfully.")  # Notify that contacts have been saved
        except Exception as e:  # In case of an error while saving the file
            print(f"Error saving contacts: {e}")  # Print the error message

    # Method to load contacts from a file
    def load_from_file(self):
        if os.path.exists(self.file_name):  # Check if the file exists
            try:
                with open(self.file_name, 'rb') as file:  # Open the file in read-binary mode
                    self.contacts = pickle.load(file)  # Deserialize and load the contacts list from the file
                print("Contacts loaded successfully.")  # Notify that contacts have been loaded
            except Exception as e:  # In case of an error while reading the file
                print(f"Error loading contacts: {e}")  # Print the error message
        else:
            print("No previous contacts found. Starting fresh.")  # Inform that no previous data exists

# Main function to drive the program
def main():
    file_name = "contacts.pkl"  # Define the file name to store contacts
    db = ContactsDatabase(file_name)  # Create an instance of the ContactsDatabase class

    while True:  # Infinite loop to show the menu until the user exits
        print("\n--- Contacts Database ---")  # Displaying the menu options
        print("1. Add Contact")  # Option to add a new contact
        print("2. List Contacts")  # Option to list all contacts
        print("3. Exit")  # Option to exit the program

        choice = input("Choose an option: ")  # Get the user's choice

        if choice == '1':  # If the user chooses to add a contact
            name = input("Enter name: ")  # Prompt for the contact's name
            phone = input("Enter phone number: ")  # Prompt for the contact's phone number
            email = input("Enter email address: ")  # Prompt for the contact's email address
            db.add_contact(name, phone, email)  # Add the contact to the database
        elif choice == '2':  # If the user chooses to list contacts
            db.list_contacts()  # Display all the contacts
        elif choice == '3':  # If the user chooses to exit
            db.save_to_file()  # Save the current contacts to the file
            print("Exiting the program...")  # Notify that the program is exiting
            break  # Exit the loop and end the program
        else:
            print("Invalid choice. Please try again.")  # If the input is invalid, ask the user to try again

# Run the main function when the script is executed
if __name__ == "__main__":
    main()

 Output

--- Contacts Database ---
1. Add Contact
2. List Contacts
3. Exit
Choose an option: 1
Enter name: John Doe
Enter phone number: 123-456-7890
Enter email address: john.doe@example.com
Contact John Doe added.

--- Contacts Database ---
1. Add Contact
2. List Contacts
3. Exit
Choose an option: 2
Name: John Doe, Phone: 123-456-7890, Email: john.doe@example.com

--- Contacts Database ---
1. Add Contact
2. List Contacts
3. Exit
Choose an option: 3
Contacts saved successfully.
Exiting the program...