como experto programador, mejora el siguiente codigo: import sqlite3
from tkinter import *
from tkcalendar import DateEntry  # Asegúrate de tener instalada la librería tkcalendar

class MedicalRecordsApp:
    def __init__(self, db_name='medical_records.db'):
        self.db_name = db_name
        self.conn = None
        self.cursor = None

        self.setup_db()
        
        self.root = Tk()
        self.root.title('Registro de Historia Médica Personal')
        self.create_widgets()
        self.root.mainloop()

    def setup_db(self):
        """Sets up the database connection and creates the table if it doesn't exist."""
        try:
            self.conn = sqlite3.connect(self.db_name)
            self.cursor = self.conn.cursor()
            self.cursor.execute('''CREATE TABLE IF NOT EXISTS medical_history
                                   (patient_name TEXT, date_of_birth DATE,
                                    address TEXT, previous_illnesses TEXT,
                                    allergies TEXT, current_medications TEXT,
                                    last_visit_date DATE)''')
            self.conn.commit()
        except sqlite3.Error as e:
            print(f"Error connecting to database: {e}")

    def create_widgets(self):
        """Creates the GUI widgets."""
        fields = [
            ('Nombre del paciente:', 'text', 'name_entry', 0),
            ('Fecha de nacimiento:', 'date', 'date_of_birth', 1),
            ('Dirección:', 'text', 'address_entry', 2),
            ('Enfermedades previas:', 'listbox', 'previous_illnesses_listbox', 3),
            ('Alergias:', 'listbox', 'allergies_listbox', 4),
            ('Medicamentos actuales:', 'listbox', 'current_medications_listbox', 5),
            ('Fecha de la última visita médica:', 'date', 'last_visit_date', 6)
        ]

        for label_text, widget_type, attr, row in fields:
            Label(self.root, text=label_text).grid(row=row, column=0, sticky=W)
            if widget_type == 'text':
                entry = Entry(self.root)
                entry.grid(row=row, column=1)
            elif widget_type == 'date':
                entry = DateEntry(self.root, date_pattern='yyyy-mm-dd')
                entry.grid(row=row, column=1)
            elif widget_type == 'listbox':
                entry = Listbox(self.root, height=5)
                entry.grid(row=row, column=1)
            setattr(self, attr, entry)

        Button(self.root, text='Guardar', command=self.save_record).grid(row=len(fields), column=0, sticky=W)

    def save_record(self):
        """Saves the record to the database."""
        try:
            patient_name = self.name_entry.get()
            date_of_birth = self.date_of_birth.get()
            address = self.address_entry.get()
            previous_illnesses = ', '.join(self.previous_illnesses_listbox.get(0, END))
            allergies = ', '.join(self.allergies_listbox.get(0, END))
            current_medications = ', '.join(self.current_medications_listbox.get(0, END))
            last_visit_date = self.last_visit_date.get()

            self.cursor.execute("INSERT INTO medical_history VALUES (?, ?, ?, ?, ?, ?, ?)",
                                (patient_name, date_of_birth, address, previous_illnesses,
                                 allergies, current_medications, last_visit_date))
            self.conn.commit()
            self.clear_entries()
        except sqlite3.Error as e:
            print(f"Error saving record: {e}")

    def clear_entries(self):
        """Clears all input fields."""
        self.name_entry.delete(0, END)
        self.address_entry.delete(0, END)
        self.previous_illnesses_listbox.delete(0, END)
        self.allergies_listbox.delete(0, END)
        self.current_medications_listbox.delete(0, END)

    def __del__(self):
        """Ensures the database connection is closed."""
        if self.conn:
            self.conn.close()

# Ejecutar la aplicación
if __name__ == '__main__':
    app = MedicalRecordsApp()