Why won't my code open the Tkinter window?

Tkinter, the renowned Python library, serves as a powerful tool for crafting visually stunning Graphical User Interfaces (GUIs) within the Python programming landscape. With its intuitive design and robust functionality, Tkinter empowers developers to create engaging and interactive user experiences seamlessly.

Essentially, after importing the Tkinter module and writing our code with labels and all the yada yada, a window, tkinter window, should pop up when we run the code. This window is a GUI output of our code.

Often times we run into a situation where our code runs without errors but the pop-up window just never comes. In a bid to figure in out, we go down an installation rabbit hole. Install XMing, another IDE, Tkinter, Matplotlib... The list goes on.

# imports
from tkinter import *
import os
from PIL import ImageTk, Image 

# main screen
master = Tk()
master.title('Pesa')

# import image
img = Image.open('banx.jpg')
img = img.resize((150, 150))
img = ImageTk.PhotoImage(img)

# labels
Label(master, text = 'Pesa Banking', font=('Calibri', 15)).grid(row=0, sticky=N, pady=10)

Here is my code sample that wouldn't open the tkinter window.

# imports
from tkinter import *
import os
from PIL import ImageTk, Image 

# main screen
master = Tk()
master.title('Pesa')

# import image
img = Image.open('banx.jpg')
img = img.resize((150, 150))
img = ImageTk.PhotoImage(img)

# labels
Label(master, text = 'Pesa Banking', font=('Calibri', 15)).grid(row=0, sticky=N, pady=10)

mainloop()

Here is a sample that does, in fact open the window.
See the difference?

For the tkinter to run and open the pop-up window, you need a mainloop() line.

In Tkinter, the mainloop() function is the essential component that enables the proper functioning of graphical user interface (GUI) applications. It establishes an infinite loop that actively listens for and handles user interactions, system events, and window management tasks. This loop ensures that the GUI application remains responsive to user input and can update the display as needed, all while allowing the program to block and wait for user actions without freezing the entire application. mainloop() is the driving force behind the interactivity and responsiveness of Tkinter-based GUIs, making it a critical part of any GUI application's structure.

Next time you are about to fall into the installing rabbit hole, remember to choeck your mainloop() function.

Happy coding:)