5 Best Ways to Create Child Windows with Python Tkinter

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πŸ’‘ Problem Formulation: In GUI programming with Python’s Tkinter, a common requirement is to spawn additional windows aside from the main application window. These secondary windows, commonly referred to as ‘child windows’ or ‘dialogs’, serve various purposes such as gathering extra information, displaying messages, or housing complex widgets separately from the main interface. The input here is a user event that demands a new window, and the desired output is a responsive, functional child window that serves a specific purpose within the application.

Method 1: Using the Toplevel widget

This method involves creating a new instance of the Toplevel class, which is a standard way to create additional windows in Tkinter. The Toplevel window acts independently of the main window, meaning it can be moved, resized, or closed without affecting the main application.

Here’s an example:

import tkinter as tk

def create_child():
    child_window = tk.Toplevel(root)
    child_window.title("Child Window")
    tk.Label(child_window, text="Welcome to the child window").pack()

root = tk.Tk()
root.title("Main Window")

tk.Button(root, text="Create Child Window", command=create_child).pack()

root.mainloop()

The output of this code snippet is a guiable main window with a button “Create Child Window”. When this button is clicked, a new child window opens with the title “Child Window” and contains a welcoming message.

This code snippet defines a main window and a function that, when called, creates a child window with a label. The function is bound to a button on the main window, so every time the button is clicked, a new child window is instantiated.

Method 2: Setting Parent-Child Relationship explicitly

This method takes advantage of the features of Tkinter that allow you to specify the master of a widget. By setting the new Toplevel window’s master to the main application window, one establishes a clear parent-child relationship.

Here’s an example:

import tkinter as tk

def create_child():
    child_window = tk.Toplevel(root)
    child_window.title("Owned by Main Window")
    child_window.transient(root)  # Set to be on top of the main window
    tk.Label(child_window, text="I'm a child owned by the main window").pack()

root = tk.Tk()
tk.Button(root, text="Create Child Window with Parent", command=create_child).pack()

root.mainloop()

This snippet results in a main application window with a button that, when clicked, produces a child window which is set transient to the main windowβ€”meaning it is always on top of the parent window.

The function transient is called on the child window with the main window as the argument, establishing a parent-child hierarchy. This makes it clear that the child window is an auxiliary window to the main window, often used for dialogs that are temporary and should not stray from the parent window.

Method 3: Using a Modal Child Window

To create a child window that blocks interaction with the main window until it’s closed (a modal window), one can disable the main window. This is useful for forcing users to complete tasks within the child window before returning to the main application.

Here’s an example:

import tkinter as tk

def create_child():
    child_window = tk.Toplevel(root)
    child_window.title("Modal Child Window")
    child_window.grab_set()  # Make the child window modal
    tk.Label(child_window, text="Please interact with me before returning to main window!").pack()
    child_window.protocol("WM_DELETE_WINDOW", lambda: close_child(child_window))

def close_child(window):
    window.grab_release()
    window.destroy()

root = tk.Tk()
tk.Button(root, text="Create Modal Child Window", command=create_child).pack()

root.mainloop()

When executed, this code creates a main window and a child window that must be interacted with and closed before returning to the main window.

This example demonstrates how to effectively create a modal dialog by calling grab_set, which confines the focus to the child window until it’s closed. The child window also has a close event binding to ensure the main window is re-enabled once the child is closed.

Method 4: Customization through Child Window Class

For applications requiring complex child windows, it’s beneficial to create a custom class that inherits from Toplevel. This allows for more organized code and reusability of the child window definitions and behavior.

Here’s an example:

import tkinter as tk

class CustomChild(tk.Toplevel):
    def __init__(self, master, **kwargs):
        super().__init__(master, **kwargs)
        self.title("Custom Child Window")
        tk.Label(self, text="This is a customized child window").pack()
        self.protocol("WM_DELETE_WINDOW", self.on_close)

    def on_close(self):
        print("Custom child window closed")
        self.destroy()

root = tk.Tk()
child = CustomChild(root)
child.mainloop()

Running this code snippet yields a main window which will immediately open a custom child window configured through the CustomChild class upon launch.

The CustomChild class defines a child window with a predefined title and label, as well as a custom close event. By encapsulating the behavior and layout in a class, one achieves a modular and cleaner design, especially beneficial in larger applications.

Bonus One-Liner Method 5: Inline Child Window Creation

This method is the most straightforward way to create a child window with just one line of code. It is useful for small applications or scripts where one quickly needs to display additional information without much customization.

Here’s an example:

import tkinter as tk

root = tk.Tk()
tk.Toplevel(root, title="Inline Child").mainloop()

After the main window initializes, this one-liner instantly spawns a child window titled “Inline Child”.

This minimal approach creates a functional child window with a title. It’s perfect for rapid prototyping or applications where child windows are not the focus and don’t require a lot of functionality or intricate design.

Summary/Discussion

    Method 1: Toplevel widget. Straightforward and practical. No special dependencies. Method 2: Explicit Parent-Child relationship. Useful for intuitive window stacking and control. Adds clarity to window hierarchy. Method 3: Modal Windows. Essential for scenarios where user input is required before returning to the primary window. Restricts flow until action is taken. Method 4: Custom Child Window Class. Offers organized, maintainable code. Ideal for complex child windows with repeated usage. Method 5: Inline Creation. Fastest method, but lacks customization and functionality for more advanced needs.