pyqt/basic/signals_and_slots_1.py

import sys

from PyQt5.QtWidgets import QMainWindow, QPushButton, QApplication


def the_button_was_clicked():
    print("Button was clicked")


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()
        self.setWindowTitle("My App")
        button = QPushButton("Press Me!")
        button.clicked.connect(the_button_was_clicked)
        # Set the central widget of the window
        self.setCentralWidget(button)


app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec_()