GUI (Graphical User Interface) development allows users to interact with applications using windows, buttons, menus, forms, and graphics instead of command-line text.

1. Introduction to GUI Programming

What is GUI?

GUI stands for Graphical User Interface.

Examples:

Calculator app
Text editor
Login form
Desktop software

Python provides several GUI libraries:

Tkinter (built-in)
PyQt
Kivy
wxPython

2. Tkinter Basics

What is Tkinter?

Tkinter is Python’s standard GUI library.

Features

Built into Python
Easy to learn
Cross-platform
Good for small/medium desktop apps

3. Creating First Tkinter Window

import tkinter as tk

root = tk.Tk()

root.title("My First App")
root.geometry("400x300")

root.mainloop()

Explanation

Tk() → creates main window
title() → window title
geometry() → window size
mainloop() → keeps window running

4. Tkinter Widgets

Widgets are GUI elements.

Common widgets:

Label
Button
Entry
Text
Checkbutton
Radiobutton
Listbox

5. Label Widget

import tkinter as tk

root = tk.Tk()

label = tk.Label(root, text="Hello Tkinter")
label.pack()

root.mainloop()

6. Button Widget

import tkinter as tk

def hello():
    print("Button Clicked")

root = tk.Tk()

btn = tk.Button(root, text="Click Me", command=hello)
btn.pack()

root.mainloop()

7. Entry Widget

import tkinter as tk

def show():
    print(entry.get())

root = tk.Tk()

entry = tk.Entry(root)
entry.pack()

btn = tk.Button(root, text="Submit", command=show)
btn.pack()

root.mainloop()

8. Text Widget

import tkinter as tk

root = tk.Tk()

text = tk.Text(root, height=5, width=30)
text.pack()

root.mainloop()

9. Geometry Managers

Used for arranging widgets.

pack()

label.pack()

grid()

label.grid(row=0, column=0)

place()

label.place(x=50, y=100)

10. Message Box

from tkinter import messagebox
import tkinter as tk

root = tk.Tk()

def show():
    messagebox.showinfo("Info", "Welcome")

btn = tk.Button(root, text="Show", command=show)
btn.pack()

root.mainloop()

11. Frames in Tkinter

Frames group widgets together.

import tkinter as tk

root = tk.Tk()

frame = tk.Frame(root)
frame.pack()

tk.Button(frame, text="Button 1").pack(side="left")
tk.Button(frame, text="Button 2").pack(side="left")

root.mainloop()

12. Event Handling in Tkinter

Events occur when user interacts with GUI.

Examples:

Mouse click
Keyboard press
Window close

13. Mouse Click Event

import tkinter as tk

def clicked(event):
    print("Mouse Clicked")

root = tk.Tk()

label = tk.Label(root, text="Click Here")
label.pack()

label.bind("<Button-1>", clicked)

root.mainloop()

14. Keyboard Event

import tkinter as tk

def key_pressed(event):
    print("Key:", event.char)

root = tk.Tk()

root.bind("<Key>", key_pressed)

root.mainloop()

15. Menu Bar

import tkinter as tk

root = tk.Tk()

menu = tk.Menu(root)
root.config(menu=menu)

file_menu = tk.Menu(menu)
menu.add_cascade(label="File", menu=file_menu)

file_menu.add_command(label="Open")
file_menu.add_command(label="Exit", command=root.quit)

root.mainloop()

16. Simple Calculator GUI

import tkinter as tk

def calculate():
    result = int(num1.get()) + int(num2.get())
    output.config(text=str(result))

root = tk.Tk()

num1 = tk.Entry(root)
num1.pack()

num2 = tk.Entry(root)
num2.pack()

btn = tk.Button(root, text="Add", command=calculate)
btn.pack()

output = tk.Label(root, text="")
output.pack()

root.mainloop()

17. Introduction to PyQt

What is PyQt?

PyQt is a powerful GUI framework based on Qt.

Advantages

Modern UI
Advanced widgets
Professional applications
Better design tools

Installation

pip install PyQt5

18. First PyQt Application

import sys
from PyQt5.QtWidgets import QApplication, QWidget

app = QApplication(sys.argv)

window = QWidget()
window.setWindowTitle("PyQt App")
window.resize(400, 300)

window.show()

sys.exit(app.exec_())

19. PyQt Widgets

Common widgets:

QLabel
QPushButton
QLineEdit
QTextEdit
QComboBox

20. Button in PyQt

import sys
from PyQt5.QtWidgets import QApplication, QPushButton

app = QApplication(sys.argv)

button = QPushButton("Click Me")
button.show()

sys.exit(app.exec_())

21. Event Handling in PyQt

import sys
from PyQt5.QtWidgets import QApplication, QPushButton

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

app = QApplication(sys.argv)

button = QPushButton("Click")
button.clicked.connect(clicked)

button.show()

sys.exit(app.exec_())

22. Layouts in PyQt

Layouts manage widget positions.

Types:

QVBoxLayout
QHBoxLayout
QGridLayout

Example:

import sys
from PyQt5.QtWidgets import (
    QApplication,
    QWidget,
    QVBoxLayout,
    QPushButton
)

app = QApplication(sys.argv)

window = QWidget()

layout = QVBoxLayout()

layout.addWidget(QPushButton("Button 1"))
layout.addWidget(QPushButton("Button 2"))

window.setLayout(layout)

window.show()

sys.exit(app.exec_())

23. Tkinter vs PyQt

Feature	Tkinter	PyQt
Built-in	Yes	No
Easy to Learn	Yes	Medium
Modern UI	Basic	Excellent
Performance	Good	Very Good
Best For	Beginners	Professional Apps

24. Mini Projects for Practice

Beginner

Calculator
Login form
To-do app
Unit converter

Intermediate

Text editor
Music player
Chat application
Image viewer

Advanced

IDE/editor
Billing software
Inventory system

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25. Best Practices

Separate GUI and logic
Use functions/classes
Validate user input
Keep UI simple
Use layouts properly

26. Summary

In this chapter you learned:

GUI fundamentals
Tkinter basics
Widgets and layouts
Event handling
PyQt basics
Building desktop applications

22. GUI Development in Python