PyQt Signal Tutorial

Welcome to this interactive tutorial on PyQt Signals. In this tutorial, you will learn how to use signals and slots in PyQt to communicate between objects in your application.

What are PyQt Signals?

In PyQt, a signal is an something that is emitted when something happens, such as a button click(s). Signals are emitted by objects and can be connected to slots. Slots are Python functions that are called in response to a signal.

Creating a Signal

To create a signal in PyQt, we use the pyqtSignal() function. The syntax for creating a signal is:

    signal = pyqtSignal(arg_type1, arg_type2, ...)

For example, the following code creates a signal named clicked that takes no arguments:

    clicked = pyqtSignal()

Connecting a Signal to a Slot(Python function)

To connect a signal to a slot(function), we use the connect() function. The syntax for connecting a signal to a slot is:

    signal.connect(slot_function)

For example, to connect the clicked signal to a slot_function, we would use the following code:

    clicked.connect(slot_function)

It's worth noting that the slot function can also accept parameters from the signal, for example:

    signal = pyqtSignal(str)

    signal.connect(slot_function)

Emitting a Signal

To emit a signal, we use the emit() function. The syntax for emitting a signal is:

    signal.emit(arg1, arg2, ...)

For example, to emit the clicked signal, we would use the following code:

    clicked.emit()

Example

Let's put everything together in a simple example. In this example, we will create a button and connect its clicked signal to a slot that prints "Button clicked".

from PyQt6.QtCore import pyqtSignal, QObject

from PyQt6.QtWidgets import QPushButton

class MyButton(QObject):

    clicked = pyqtSignal()

    

    def __init__(self):

        super().__init__()

        self.button = QPushButton("Click me")

 

self.button.clicked.connect(self.clicked.emit) def slot_function(): print("Button clicked")

In this example, we first create a custom button class called MyButton which inherits from QObject. Within this class, we create a signal called clicked using the pyqtSignal() function. We then create an instance of the button, and connect it's clicked signal to emit the clicked signal we created in the MyButton class.

Next, we define the slot_function that will be called when the clicked signal is emitted. In this case, all it does is print "Button clicked".

Finally, to use this class and connect the signal to the slot, you would use the following code:

my_button = MyButton()

my_button.clicked.connect(slot_function)

Now, every time the button created in the MyButton class is clicked, it will emit the clicked signal, which will in turn call the slot_function.

Summary

In this tutorial, you learned the basics of signals and slots in PyQt. You learned how to create signals and slots, connect them together, and emit signals. With this knowledge, you should be able to create responsive and dynamic PyQt applications that can handle user input and other events.

I hope you found this tutorial helpful. If you have any questions or comments, please feel free to leave them below.

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