Python GUI Development: wxPython, PyQT, Tkinter, Kivy

Introduction
Prerequisites
Overview
wxPython
PyQT
Tkinter
Kivy
Conclusion

Introduction

In this tutorial, we will explore different graphical user interface (GUI) development options for Python. GUI frameworks are essential for creating interactive applications with buttons, menus, and other visual elements. We will focus on four popular GUI libraries: wxPython, PyQT, Tkinter, and Kivy. By the end of this tutorial, you will have a good understanding of these libraries and will be able to choose the one that suits your needs.

Prerequisites

To follow this tutorial, you should have a basic understanding of Python programming language and its syntax. Familiarity with object-oriented programming (OOP) concepts will also be helpful. Additionally, make sure you have Python installed on your system. You can download the latest version of Python from the official Python website.

Overview

Before diving deep into each GUI library, let’s have a brief overview of each one:

wxPython: This library is a Python wrapper for the popular wxWidgets C++ library. It provides a native look and feel across different platforms and has an extensive set of widgets and tools for building desktop applications.
PyQT: PyQT is a set of Python bindings for the Qt application framework. It offers all the benefits of Qt, including comprehensive GUI functionality, cross-platform compatibility, and support for rapid application development. PyQT is a great choice for creating complex and professional-looking applications.
Tkinter: Tkinter is the standard GUI toolkit for Python. It provides a simple and intuitive way to create GUI applications. Tkinter comes bundled with Python, so no additional installation is required. It may not be as feature-rich as the other libraries, but it is lightweight and easy to learn.
Kivy: Kivy is an open-source Python library for developing multitouch applications. It uses OpenGL to provide an engaging and modern user interface. Kivy is cross-platform and supports touch, mouse, and keyboard input. It is an excellent option for building applications with a unique and interactive user experience.

Now, let’s explore each library in more detail.

wxPython

wxPython is a powerful and flexible GUI toolkit for Python. It allows you to create native-looking applications with a wide range of widgets, such as buttons, menus, text controls, and more. Here are the steps to get started with wxPython:

Installation: To install wxPython, you can use pip, the Python package manager. Open your command line or terminal and run the following command:
```
pip install wxPython
```
Hello World: Let’s start with a simple “Hello, World!” application. Create a new Python script and import the wx package:
```
import wx
```
Next, create an application object and a top-level window:
```
app = wx.App()
frame = wx.Frame(None, title="Hello, World!")
```
Add a label widget to the frame to display the message:
```
label = wx.StaticText(frame, label="Hello, World!")
```
Finally, show the window and start the application’s main event loop:
```
frame.Show()
app.MainLoop()
```
Run the script, and you should see a window with the “Hello, World!” message.

Note: Make sure to include the app.MainLoop() call at the end; otherwise, your application won’t respond to events.
Adding Interactivity: You can make your GUI application interactive by responding to user actions, such as button clicks. Let’s add a button to our “Hello, World!” application that changes the message when clicked.
```
button = wx.Button(frame, label="Click me")

def on_button_click(event):
    label.SetLabel("Button clicked!")

button.Bind(wx.EVT_BUTTON, on_button_click)
```
In this example, we create a button widget and define a callback function on_button_click that changes the label’s text when called. We then bind the button’s wx.EVT_BUTTON event to the callback function using the Bind method.
Layout Management: wxPython provides different types of layout managers to organize widgets within a window. For example, you can use sizers to automatically position and size widgets based on predefined rules.
```
panel = wx.Panel(frame)
sizer = wx.BoxSizer(wx.VERTICAL)
sizer.Add(label, proportion=1, flag=wx.EXPAND)
sizer.Add(button)
panel.SetSizer(sizer)
```
In this code snippet, we create a panel widget and a vertical box sizer. We add the label and button widgets to the sizer using the Add method, specifying their proportions and flags. Finally, we set the panel’s sizer using the SetSizer method.
Common Controls: wxPython provides a wide range of common controls, including checkboxes, radio buttons, listboxes, and more. You can explore the wxPython documentation to learn more about each control and its properties.

Here’s an example of adding a checkbox control to our application:
```
checkbox = wx.CheckBox(frame, label="Check me")

def on_checkbox_toggle(event):
    if checkbox.GetValue():
        label.SetLabel("Checkbox checked!")
    else:
        label.SetLabel("Checkbox unchecked!")

checkbox.Bind(wx.EVT_CHECKBOX, on_checkbox_toggle)
```
In this case, we create a checkbox widget and define a callback function on_checkbox_toggle that changes the label’s text based on the checkbox’s value. We bind the widget’s wx.EVT_CHECKBOX event to the callback function.

PyQT

PyQT is a robust toolkit for building interactive and professional-looking GUI applications in Python. It provides a large collection of widgets, highly customizable styles, and support for various platforms. Here’s how you can start using PyQT:

Installation: To install PyQT, you can use pip by running the following command in your command line or terminal:
```
pip install pyqt5
```
Hello World: Let’s create a “Hello, World!” application with PyQT. Create a new Python script and import the necessary classes:
```
from PyQt5.QtWidgets import QApplication, QLabel, QMainWindow

app = QApplication([])
window = QMainWindow()
```
Next, create a label widget with the desired message:
```
label = QLabel("Hello, World!", parent=window)
window.setCentralWidget(label)
```
Finally, show the window and start the application’s event loop:
```
window.show()
app.exec()
```
Run the script, and you should see a window with the “Hello, World!” message.

Note: Make sure to include the app.exec() call at the end to start the application’s event loop.
Adding Interactivity: You can make your PyQT application interactive by connecting signals (events) to slots (callbacks). Let’s add a button to our “Hello, World!” application that changes the message when clicked.
```
from PyQt5.QtWidgets import QPushButton

button = QPushButton("Click me", parent=window)

def on_button_click():
    label.setText("Button clicked!")

button.clicked.connect(on_button_click)
```
In this example, we create a button widget and define a callback function on_button_click that changes the label’s text. We connect the button’s clicked signal to the callback function using the connect method.
Layout Management: PyQT provides a variety of layout managers for organizing widgets within a window. For example, you can use QVBoxLayout or QHBoxLayout to create vertical or horizontal layouts, respectively.
```
from PyQt5.QtWidgets import QVBoxLayout

layout = QVBoxLayout()
layout.addWidget(label)
layout.addWidget(button)
window.setLayout(layout)
```
In this code snippet, we create a vertical layout and add the label and button widgets to it using the addWidget method. Finally, we set the window’s layout using the setLayout method.
Common Controls: PyQT offers a wide range of built-in widgets, including checkboxes, radio buttons, listboxes, and more. You can refer to the PyQT documentation to learn more about each widget and its properties.

Here’s an example of adding a checkbox control to our application:
```
from PyQt5.QtWidgets import QCheckBox

checkbox = QCheckBox("Check me", parent=window)

def on_checkbox_toggle(checked):
    if checked:
        label.setText("Checkbox checked!")
    else:
        label.setText("Checkbox unchecked!")

checkbox.toggled.connect(on_checkbox_toggle)
```
In this case, we create a checkbox widget and define a callback function on_checkbox_toggle that changes the label’s text based on the checkbox’s state. We connect the widget’s toggled signal to the callback function.

Tkinter

Tkinter is the standard GUI toolkit for Python and comes bundled with Python itself. It provides a simple and intuitive way to create GUI applications. Here’s how you can get started with Tkinter:

Hello World: Let’s create a “Hello, World!” application using Tkinter. Create a new Python script and import the tkinter module:
```
import tkinter as tk

root = tk.Tk()
```
Next, create a label widget with the desired message:
```
label = tk.Label(root, text="Hello, World!")
label.pack()
```
Finally, start the application’s main event loop:
```
root.mainloop()
```
Run the script, and you should see a window with the “Hello, World!” message.
Adding Interactivity: You can make your Tkinter application interactive by defining callback functions and associating them with events. Let’s add a button to our “Hello, World!” application that changes the message when clicked.
```
button = tk.Button(root, text="Click me")

def on_button_click():
    label.config(text="Button clicked!")

button.config(command=on_button_click)
```
In this example, we create a button widget and define a callback function on_button_click that changes the label’s text. We configure the button’s command attribute to execute the callback function when clicked.
Layout Management: Tkinter provides different geometry managers for organizing widgets within a window. For example, you can use the pack method to automatically position and size widgets based on the available space.
```
button.pack(side="bottom")
```
In this code snippet, we use the side parameter to specify the position of the button. We can set it to “bottom,” “top,” “left,” or “right” to place the button accordingly.
Common Controls: Tkinter offers a variety of common controls, such as checkboxes, radio buttons, listboxes, and more. Each control is represented by a specific widget class, which you can create and customize as needed. You can consult the Tkinter documentation for more details on each control and its properties.

Here’s an example of adding a checkbox control to our application:
```
checkbox = tk.Checkbutton(root, text="Check me")

def on_checkbox_toggle():
    if checkbox.var.get() == 1:
        label.config(text="Checkbox checked!")
    else:
        label.config(text="Checkbox unchecked!")

checkbox.var = tk.IntVar()
checkbox.config(variable=checkbox.var, command=on_checkbox_toggle)
```
In this case, we create a checkbox widget and define a callback function on_checkbox_toggle that changes the label’s text based on the checkbox’s value. We associate the checkbox with an IntVar and configure its variable and command attributes accordingly.

Kivy

Kivy is an open-source Python library for developing multitouch applications with a modern and engaging user interface. It leverages OpenGL for hardware acceleration and provides a rich set of tools for building cross-platform applications. Let’s explore how to use Kivy:

Installation: To install Kivy, you can use pip by running the following command in your command line or terminal:
```
pip install kivy
```

Hello World: Let’s create a “Hello, World!” application with Kivy. Create a new Python script and import the necessary classes:

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout

Next, define a custom App class and its build method:

class HelloWorldApp(App):
    def build(self):
        layout = BoxLayout()
        label = Label(text="Hello, World!")
        layout.add_widget(label)
        return layout

Finally, create an instance of the app and run it:

HelloWorldApp().run()

Run the script, and you should see a window with the “Hello, World!” message.

Adding Interactivity: You can make your Kivy application interactive by defining event handlers and binding them to specific events. Let’s add a button to our “Hello, World!” application that changes the message when clicked.

from kivy.uix.button import Button

class HelloWorldApp(App):
    def build(self):
        layout = BoxLayout(orientation="vertical")
        label = Label(text="Hello, World!")
        button = Button(text="Click me")

        def on_button_click(instance):
            label.text = "Button clicked!"

        button.bind(on_press=on_button_click)
        layout.add_widget(label)
        layout.add_widget(button)
        return layout

In this example, we create a button widget and define a callback function on_button_click that changes the label’s text. We bind the button’s on_press event to the callback function using the bind method.

Layout Management: Kivy provides various layout classes for organizing widgets within a window. For example, you can use BoxLayout, FloatLayout, or GridLayout to arrange widgets horizontally, with floating positions, or in a grid, respectively.

from kivy.uix.gridlayout import GridLayout

class HelloWorldApp(App):
    def build(self):
        layout = GridLayout(cols=2)
        label = Label(text="Hello, World!")
        button = Button(text="Click me")
        layout.add_widget(label)
        layout.add_widget(button)
        return layout

In this code snippet, we create a GridLayout with two columns and add the label and button widgets to it using the add_widget method.

Common Controls: Kivy offers various UI elements, such as checkboxes, radio buttons, sliders, and more. You can refer to the Kivy documentation to learn more about each control and its properties.

Here’s an example of adding a checkbox control to our application:

from kivy.uix.checkbox import CheckBox

class HelloWorldApp(App):
    def build(self):
        layout = BoxLayout(orientation="vertical")
        label = Label(text="Hello, World!")
        checkbox = CheckBox(active=False)

        def on_checkbox_toggle(instance, value):
            if value:
                label.text = "Checkbox checked!"
            else:
                label.text = "Checkbox unchecked!"

        checkbox.bind(active=on_checkbox_toggle)
        layout.add_widget(label)
        layout.add_widget(checkbox)
        return layout

In this case, we create a checkbox widget and define a callback function on_checkbox_toggle that changes the label’s text. We bind the checkbox’s active property to the callback function using the bind method.

Conclusion

In this tutorial,

Published: 22 December 2020