Python! GUI Apps with Tkinter | Lectures 20

Let’s Start Python Programming For Beginners to Advanced. Intro to GUI Apps with Tkinter, Lectures 20

🐍 Lecture 20: Intro to GUI Apps with Tkinter

🎯 Goal

By the end of this lecture, you will:

• Understand what a GUI (Graphical User Interface) is.
• Be able to create windows, buttons, and labels using Tkinter.
• Know how to handle button clicks and update text on the screen.
• Build a simple calculator GUI or a click counter app.

🧠 What Is a GUI?

So far, we’ve been writing programs that run in the command line, where everything is text-based.

A GUI (Graphical User Interface) lets users interact with buttons, windows, and images, just like real apps!

📱 Think of your phone:

• You tap buttons
• You see icons and text
• You don’t type commands

We’ll use Python’s built-in module called tkinter to make our own GUI apps.

🛠️ Setting Up – Import Tkinter

Start by importing tkinter:

import tkinter as tk

Then create a main window:

window = tk.Tk()
window.title("My First GUI App")
window.geometry("300x200")  # Width x Height

To start the app, run:

window.mainloop()

This creates a basic empty window. Now let’s add things to it!

🔳 Adding Labels

A label shows text on the screen.

label = tk.Label(window, text="Hello, GUI!")
label.pack()  # Places the label in the window

You can change the font, color, and size, too:

label = tk.Label(window, text="Welcome to GUI World!", font=("Arial", 14), fg="blue")
label.pack()

🟢 Buttons – Making Things Happen

A button does something when clicked.

Let’s define a function and connect it to a button:

def say_hello():
    print("Button clicked!")
    label.config(text="You clicked the button!")

button = tk.Button(window, text="Click Me", command=say_hello)
button.pack()

Now, when you click the button, it changes the label text!

🧠 Remember:

• def defines a function.
• command= tells the button which function to run.

🧪 Try It Yourself!

Write a program that:

1. Shows a label saying “Score: 0”
2. Has a button that increases the score by 1 each time it’s clicked.

💡 Sample Code:

score = 0

def increase_score():
    global score
    score += 1
    score_label.config(text=f"Score: {score}")

window = tk.Tk()
window.title("Clicker Game")
window.geometry("300x200")

score_label = tk.Label(window, text="Score: 0", font=("Arial", 16))
score_label.pack()

button = tk.Button(window, text="Click to Increase Score", command=increase_score)
button.pack()

window.mainloop()

🧱 Building a Simple Calculator GUI

Let’s build a simple calculator with two buttons: one adds 1, one subtracts 1.

value = 0

def add_one():
    global value
    value += 1
    update_label()

def subtract_one():
    global value
    value -= 1
    update_label()

def update_label():
    number_label.config(text=str(value))

window = tk.Tk()
window.title("Simple Calculator")
window.geometry("200x150")

number_label = tk.Label(window, text="0", font=("Arial", 24))
number_label.pack()

add_button = tk.Button(window, text="+1", command=add_one, width=10)
add_button.pack(pady=5)

subtract_button = tk.Button(window, text="-1", command=subtract_one, width=10)
subtract_button.pack(pady=5)

window.mainloop()

👉 This shows how to:

• Update a label dynamically
• Use spacing with pady=5
• Create interactive buttons

🚀 Challenge (Optional)

Make a color changer app that:

• Has a label showing the current color name.
• Two buttons: one for changing to red, another to blue.
• Changes background color and text accordingly.

Example:

def set_red():
    color_label.config(text="Red", fg="red", bg="lightcoral")

def set_blue():
    color_label.config(text="Blue", fg="blue", bg="lightblue")

window = tk.Tk()
window.title("Color Changer")
window.geometry("250x200")

color_label = tk.Label(window, text="Choose a color", font=("Arial", 18))
color_label.pack(pady=20)

red_button = tk.Button(window, text="Red", command=set_red, width=10)
red_button.pack(pady=5)

blue_button = tk.Button(window, text="Blue", command=set_blue, width=10)
blue_button.pack(pady=5)

window.mainloop()

🧒 Kids Corner

🧠 Imagine your robot friend now has a face — with eyes, mouth, and buttons it can press!

🤖 Robot says:

Beep! I can see buttons now and click them with my mouse!

📌 Summary

• A GUI lets users interact with buttons, labels, and windows.
• Use tkinter to create GUI apps in Python.
• Add labels with tk.Label(), buttons with tk.Button().
• Connect functions to buttons using command=.
• GUI programming makes your apps feel like real software!

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