PyQt Signals let you react to user input such as mouse clicks. A slot is a function that gets called when such an event occurs. The file main.py in this directory shows this in action: When the user clicks a button, a popup appears:

The code begins in the usual way. First, we import PyQt6 and create a QApplication:

from PyQt6.QtWidgets import *
app = QApplication([])

Next, we create a button:

button = QPushButton('Click')

Then we define a function. It will be called when the user clicks the button. You can see that it shows an alert:

def on_button_clicked():
    alert = QMessageBox()
    alert.setText('You clicked the button!')
    alert.exec()

And here is where signals and slots come into play: We instruct Qt to invoke our function by connecting it to the .clicked signal of our button:

button.clicked.connect(on_button_clicked)

Finally, we show the button on the screen and hand control over to Qt:

button.show()
app.exec()

For instructions how you can run this example yourself, please see here.