Persistencia de datos de ciudadades - Python Programming Exercise

import sqlite3


class City:
    """Represents a city with a name and population."""

    def __init__(self, name, population):
        """Initialize the city with a name and population."""
        self.name = name
        self.population = population

    def __str__(self):
        """Return a string representation of the city."""
        return f"City: {self.name}, Population: {self.population}"


class CityDatabase:
    """Manages a database of cities."""

    def __init__(self, db_name="cities.db"):
        """Initialize the database connection and create the table if necessary."""
        self.db_name = db_name
        self.connection = sqlite3.connect(self.db_name)
        self.cursor = self.connection.cursor()
        self._create_table()

    def _create_table(self):
        """Create the cities table if it does not exist."""
        self.cursor.execute("""
            CREATE TABLE IF NOT EXISTS cities (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                name TEXT NOT NULL,
                population INTEGER NOT NULL
            )
        """)
        self.connection.commit()

    def add_city(self, city):
        """Add a new city to the database."""
        self.cursor.execute("INSERT INTO cities (name, population) VALUES (?, ?)", (city.name, city.population))
        self.connection.commit()

    def get_all_cities(self):
        """Retrieve all cities from the database."""
        self.cursor.execute("SELECT name, population FROM cities")
        rows = self.cursor.fetchall()
        return [City(name, population) for name, population in rows]

    def delete_city(self, city_name):
        """Delete a city from the database by its name."""
        self.cursor.execute("DELETE FROM cities WHERE name = ?", (city_name,))
        self.connection.commit()

    def update_city_population(self, city_name, new_population):
        """Update the population of a city."""
        self.cursor.execute("UPDATE cities SET population = ? WHERE name = ?", (new_population, city_name))
        self.connection.commit()

    def close(self):
        """Close the database connection."""
        self.connection.close()


# Test Program
if __name__ == "__main__":
    # Initialize the database
    db = CityDatabase()

    # Add new cities
    print("Adding cities to the database...")
    db.add_city(City("New York", 8419000))
    db.add_city(City("Los Angeles", 3980000))
    db.add_city(City("Chicago", 2716000))

    # Retrieve and display all cities
    print("\nCurrent cities in the database:")
    for city in db.get_all_cities():
        print(city)

    # Update a city's population
    print("\nUpdating population of Los Angeles...")
    db.update_city_population("Los Angeles", 4000000)

    # Retrieve and display all cities again
    print("\nCities after update:")
    for city in db.get_all_cities():
        print(city)

    # Delete a city
    print("\nDeleting Chicago...")
    db.delete_city("Chicago")

    # Retrieve and display all cities after deletion
    print("\nCities after deletion:")
    for city in db.get_all_cities():
        print(city)

    # Close the database
    db.close()

 Output

Updating population of Los Angeles...

Cities after update:
City: New York, Population: 8419000
City: Los Angeles, Population: 4000000
City: Chicago, Population: 2716000