main.py

from PyQt5.QtCore import pyqtSlot, QRegExp
from PyQt5.QtGui import QFont, QRegExpValidator
from PyQt5.QtWidgets import (QApplication,
                             QDialog,
                             QLineEdit,
                             QMessageBox,
                             QGridLayout,
                             QListWidget)
from PyQt5.QtWidgets import QPushButton
import sys
import db_config
from datetime import datetime

class Window(QDialog):

    def __init__(self):
        super().__init__()
        self.setWindowTitle('miko learns PyQt5')
        self.setGeometry(100, 200, 400, 400)

        self.status_bar = QListWidget()
        self.status_bar.setFont(QFont('Fira Code'))
        self.status_bar.setMaximumHeight(20)

        self.q_grid = QGridLayout()
        self.q_grid.addWidget(self.status_bar)
        self.add_fields()
        self.add_buttons()

        self.list_widget = QListWidget()
        self.list_widget.setFont(QFont('Fira Code'))
        self.q_grid.addWidget(self.list_widget)
        self.window().setLayout(self.q_grid)
        self.show()

    def add_buttons(self):
        self.connect_button = QPushButton('Connect', self)
        self.connect_button.clicked.connect(self.connect_db)
        self.connect_button.move(-5, 50)

        self.disconnect_button = QPushButton('Disconnect', self)
        self.disconnect_button.clicked.connect(self.disconnect_db)
        self.disconnect_button.move(80, 50)

        self.q_grid.addWidget(self.connect_button)
        self.q_grid.addWidget(self.disconnect_button)

    def add_fields(self):
        self.host_textbox = QLineEdit(self)
        self.host_textbox.setPlaceholderText('host')
        self.host_textbox.setValidator(QRegExpValidator(QRegExp('[a-zA-Z0-9]{,40}')))

        self.database_textbox = QLineEdit(self)
        self.database_textbox.move(0, 25)
        self.database_textbox.setPlaceholderText('database')
        self.database_textbox.setValidator(QRegExpValidator(QRegExp('[a-zA-Z0-9_]{,40}')))

        self.q_grid.addWidget(self.host_textbox)
        self.q_grid.addWidget(self.database_textbox)

    @pyqtSlot()
    def disconnect_db(self):
        db_config.disconnect()
        self.list_widget.addItem(f'Disconnected from {db_config.database} at {datetime.now().time().strftime("%X")}. Version=8.0.19 ')
        self.status_bar.clear()
        self.status_bar.addItem(f'Disconnected from {db_config.database}')
        QMessageBox.about(self, 'Connection closed', 'Connection closed')

    @pyqtSlot()
    def connect_db(self):
        new_conn_data = dict()
        new_conn_data['host'] = self.host_textbox.text()
        new_conn_data['db'] = self.database_textbox.text()
        is_connected = db_config.reconnect(new_conn_data)
        if not is_connected:
            self.list_widget.addItem(f'Failed to connect to {db_config.database} at {datetime.now().time().strftime("%X")}. Version=8.0.19')
            QMessageBox.warning(self, 'Connection error', '<span style="color: red;">Invalid data</span>')
        elif new_conn_data['db'] and new_conn_data['host']:
            self.list_widget.addItem(f'Connected to {db_config.database} at {datetime.now().time().strftime("%X")}. Version=8.0.19')
            self.status_bar.clear()
            self.status_bar.addItem(f'Connected to {db_config.database}')
            QMessageBox.about(self, 'Successful connection', f'Connected to <span style="color: green;">{self.database_textbox.text()}</span>')


if __name__ == '__main__':
    App = QApplication(sys.argv)
    window = Window()
    sys.exit(App.exec())