import sys

from PyQt6.QtCore import QSize
from PyQt6.QtWidgets import QApplication, QMainWindow, QPushButton


# Subclass QMainWindow to customize your application's main window
class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("My App")

        button = QPushButton("Press Me!")

        self.setFixedSize(QSize(400, 300))  # <1>

        # Set the central widget of the Window.
        self.setCentralWidget(button)


app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec()
