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GUI Programming with Tkinter (Python)

Definition

GUI (Graphical User Interface) programming allows users to interact with software using visual elements such as windows, buttons, labels, text boxes, and menus instead of typing commands.

Tkinter is Python’s built-in library for creating GUI applications.

Key Points

1. What is GUI?

Software applications are usually developed in three phases:

  1. Understanding the problem
  2. Designing the solution
  3. Implementing the solution

A GUI application uses graphical components such as:

  • Windows
  • Buttons
  • Labels
  • Text fields
  • Message boxes

Example: A flight reservation system, calculator, or bank system can be created using GUI.

2. What is Tkinter?

Tkinter is Python’s standard GUI package.

It acts as an interface between Python and the Tk GUI toolkit.

Key facts:

  • Built into Python (no installation needed)
  • Easy to create windows and GUI elements
  • Used to make desktop applications

Import Tkinter:

from tkinter import *

3. Creating a Window

To create a GUI window:

  1. Create the main window using Tk()
  2. Set title
  3. Set size using geometry()
  4. Run the application using mainloop()

Example / Code

from tkinter import *

window = Tk()

window.title("Bank Account")
window.geometry("400x350")

window.mainloop()

Explanation

Tk()

Creates the main application window.

title()

Sets the title of the window.

geometry()

Sets the window size.

Format:

"widthxheight"

Example:

"400x350"

means:

  • Width = 400
  • Height = 350

mainloop()

Keeps the window open and running.

Output (if any)

A window appears with:

  • Title: Bank Account
  • Size: 400 × 350

4. Adding Labels

A Label is used to display text in a GUI.

Example / Code

from tkinter import *

window = Tk()

window.title("Bank Account")
window.geometry("400x350")

label1 = Label(window, text="Account Number")
label1.pack()

window.mainloop()

Explanation

Label()

Syntax:

Label(parent_window, text="Text Here")

Example:

Label(window, text="Account Number")

Creates a label with text.

pack()

Places the label automatically inside the window.

Output (if any)

A label saying:

Account Number

appears in the window.

5. Setting Size of Text in Labels

You can change text size using the font property.

Example / Code

from tkinter import *

window = Tk()

window.geometry("400x350")

label1 = Label(
    window,
    text="Bank Account",
    font=("Arial", 20)
)

label1.pack()

window.mainloop()

Explanation

font=("Arial", 20)

means:

  • Font style = Arial
  • Font size = 20

Output (if any)

Large text:

Bank Account

appears.

6. Setting Locations of Components

To place GUI elements at exact positions, we use:

place()

It uses x and y coordinates.

Example / Code

from tkinter import *

window = Tk()
window.geometry("400x350")

label1 = Label(window, text="Username")
label1.place(x=50, y=100)

window.mainloop()

Explanation

place(x=50, y=100)

means:

  • Move 50 pixels horizontally
  • Move 100 pixels vertically

This gives precise control over positioning.

Output (if any)

The label appears at a fixed position.

7. Adding Buttons

Buttons allow users to perform actions.

Example / Code

from tkinter import *

window = Tk()

window.geometry("400x350")

button1 = Button(window, text="Submit")
button1.place(x=150, y=200)

window.mainloop()

Explanation

Button()

Syntax:

Button(parent, text="Button Text")

Creates a clickable button.

Output (if any)

A Submit button appears.

8. Adding Entry Fields

Entry fields are used to take input from the user.

Example / Code

from tkinter import *

window = Tk()

window.geometry("400x350")

label1 = Label(window, text="Name")
label1.place(x=50, y=50)

entry1 = Entry(window)
entry1.place(x=150, y=50)

window.mainloop()

Explanation

Entry()

Creates a text input box.

User can type data into it.

Example:

entry1.get()

Gets the value entered by the user.

Output (if any)

A text field appears where the user can type.

9. Message Boxes

A Message Box is used to show information, warnings, or errors.

Example / Code

from tkinter import *
from tkinter import messagebox

def show_message():
    messagebox.showinfo(
        "Success",
        "Account Created Successfully"
    )

window = Tk()

window.geometry("400x350")

button1 = Button(
    window,
    text="Create Account",
    command=show_message
)

button1.pack()

window.mainloop()

Explanation

messagebox.showinfo()

Shows a popup message.

Format:

messagebox.showinfo(title, message)

command=show_message

Runs the function when button is clicked.

Output (if any)

When button is clicked:

A popup appears:

Success
Account Created Successfully

Practice 1: Bank Account Window

Example / Code

from tkinter import *

window = Tk()

window.title("Bank Account")
window.geometry("400x350")

title_label = Label(
    window,
    text="Bank Account",
    font=("Arial", 18)
)
title_label.place(x=120, y=20)

label1 = Label(window, text="Account Number")
label1.place(x=50, y=100)

label2 = Label(window, text="Account Holder")
label2.place(x=50, y=140)

window.mainloop()

Practice 2: Entry + Button Window

Example / Code

from tkinter import *
from tkinter import messagebox

def submit():
    name = entry1.get()

    messagebox.showinfo(
        "Information",
        f"Hello {name}"
    )

window = Tk()

window.title("User Form")
window.geometry("400x350")

label1 = Label(window, text="Enter Name")
label1.place(x=50, y=100)

entry1 = Entry(window)
entry1.place(x=150, y=100)

button1 = Button(
    window,
    text="Submit",
    command=submit
)
button1.place(x=150, y=150)

window.mainloop()

Common Mistakes

1. Forgetting mainloop()

Wrong:

window = Tk()

Correct:

window.mainloop()

Without it, the window closes immediately.

2. Wrong geometry format

Wrong:

window.geometry(400,350)

Correct:

window.geometry("400x350")

Must be inside quotes.

3. Forgetting parent window

Wrong:

Label(text="Hello")

Correct:

Label(window, text="Hello")

4. Forgetting command=

Wrong:

Button(window, text="Click")

Correct:

Button(window, text="Click", command=myFunction)

Short Exam Notes (very concise revision points)

  • GUI = Graphical User Interface.
  • Tkinter = Python’s built-in GUI library.
  • Import Tkinter:
from tkinter import *
  • Tk() → create window
  • title() → set title
  • geometry() → set size
  • Label() → display text
  • Button() → clickable button
  • Entry() → input field
  • place(x,y) → exact position
  • messagebox.showinfo() → popup message
  • mainloop() → keeps GUI running