import sys
from PyQt5.QtWidgets import QApplication, QLabel, QMainWindow
from PyQt5.QtCore import Qt

class HelloWorldWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Hello World App")
        self.setGeometry(100, 100, 400, 200)
        label = QLabel("Hello World", self)
        label.setAlignment(Qt.AlignCenter)
        self.setCentralWidget(label)

app = QApplication(sys.argv)
window = HelloWorldWindow()
window.show()
sys.exit(app.exec_())