Open a New Window with a Button in Python - Tkinter

Tkinter is the most commonly used GUI (Graphical User Interface) library in Python. It is simple, easy to learn and comes built-in with Python. The name "Tkinter" comes from the tk interface, which is the underlying toolkit it uses.

To create multiple windows in a Tkinter application, we use the Toplevel widget. It functions similarly to a Frame, but it opens in a separate window with properties like a title bar, minimize, maximize and close buttons, just like the main application window.

What is the Toplevel Widget

• Toplevel is used to create a new independent window in a Tkinter application.
• It acts like the main window, having its own title bar, minimize, maximize and close buttons.
• It can be used for pop-ups, dialogs or additional windows in the application.

In this guide, we will explore how to open a new window when a button is clicked using two approaches:

1. Using a function to create a new window
2. Using a class-based approach for better modularity

Setting Up Tkinter

Tkinter comes pre-installed with Python. However, on some Linux distributions like Ubuntu, we may need to install it using: 

sudo apt-get install python-tk 

Creating a New Window Using a Function

This approach creates a new window when a button is clicked using the Toplevel widget. Here is the code:

from tkinter import * from tkinter.ttk import * # Create the main window master = Tk() master.geometry("300x200") # Set window size master.title("Main Window") # Function to open a new window def open_new_window(): new_window = Toplevel(master) # Create a new window new_window.title("New Window") new_window.geometry("250x150") Label(new_window, text="This is a new window").pack(pady=20) # Create a label and a button to open the new window Label(master, text="This is the main window").pack(pady=10) Button(master, text="Open New Window", command=open_new_window).pack(pady=10) # Run the Tkinter event loop master.mainloop() 

Output: 

Explanation:

• Toplevel(master): Creates a new window that is independent of the main window.
• new_window.title("New Window"): Sets the window title.
• new_window.geometry("250x150"): Defines the size of the new window.
• Label(...).pack(): Displays text inside the new window.
• command=open_new_window: Calls the function when the button is clicked.

Using a Class-Based Approach

This approach creates a dedicated class for new windows, making the code more reusable and organized. Here is the code:

from tkinter import * from tkinter.ttk import * # Class for creating a new window class NewWindow(Toplevel): def __init__(self, master=None): super().__init__(master) self.title("New Window") self.geometry("250x150") Label(self, text="This is a new window").pack(pady=20) # Create the main window master = Tk() master.geometry("300x200") master.title("Main Window") Label(master, text="This is the main window").pack(pady=10) # Create a button to open the new window using the class btn = Button(master, text="Open New Window") btn.bind("<Button>", lambda e: NewWindow(master)) # Bind the event btn.pack(pady=10) # Run the Tkinter event loop master.mainloop() 

Output: 

Explanation:

1. Class-Based Window (NewWindow)

• Inherits from Toplevel, so every instance behaves as a separate window.
• Defines window properties like title, size and a label inside the window.

2. Binding Click Event (bind()): Instead of using command=, we use .bind("<Button>", lambda e: NewWindow(master)), meaning the button click event creates a new window.