Скачать или смотреть Understanding Why You See Two Windows in Tkinter Applications

A detailed explanation of why two Tkinter windows appear when coding an application and how to manage them effectively.
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This video is based on the question https://stackoverflow.com/q/75270618/ asked by the user 'Fire Frekox' ( https://stackoverflow.com/u/20668655/ ) and on the answer https://stackoverflow.com/a/75271171/ provided by the user 'Bryan Oakley' ( https://stackoverflow.com/u/7432/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Why Do You See Two Windows in Tkinter Applications?

When developing applications with Tkinter, a common issue that users encounter is the appearance of multiple windows when they only intend to show one. If you have ever found yourself asking, "Why are there two windows opened here?" you are certainly not alone. In this guide, we will delve into this phenomenon and provide a clear understanding of why it happens and how to manage your Tkinter windows more effectively.

The Problem: Unwanted Multiple Windows

Imagine you are working on a Tkinter application and you have the following goal:

Open a window (let's call it window1).

Close window1 when a button is clicked.

Open a second window (let's call it window2) when the button is clicked.

Let’s take a look at the code snippet that often leads to confusion:

[[See Video to Reveal this Text or Code Snippet]]

In this code, when you run the program, you will see both x1 and x2 opened simultaneously. Let's break down why this happens.

The Explanation: The Role of mainloop

What Is mainloop?

In Tkinter, the mainloop() method is crucial as it starts the Tkinter event loop, allowing the application to respond to user inputs. Here’s how it works:

When you call mainloop() on a window object, that window becomes active and is visible to the user.

Why Two Windows Are Created

When you execute the code above, you are calling mainloop() for both x1 and x2 windows. Here’s the sequence of events:

Creating Two Instances: x1 = Tk() creates the first window, while x2 = Tk() creates another, independent window instance.

Calling mainloop(): When you call x1.mainloop(), it activates the first window. However, prior to this, the second window x2 already exists in memory and will be displayed when its mainloop() is invoked. Since both windows are created and no explicit control exists to manage their visibility, you will see both at once.

A Common Solution

To achieve the desired functionality—where only one window is visible at a time—you can modify your function like this:

[[See Video to Reveal this Text or Code Snippet]]

By creating x2 inside your function, you ensure that it only starts after the first window has been closed.

Conclusion: Mastering Tkinter Windows

Understanding how Tkinter’s window management works is essential for creating intuitive user interfaces. The key takeaway from this discussion is that a single call to mainloop() can activate multiple windows if they are created before the event loop is called.

To prevent unwanted windows, always ensure proper management by either destroying or creating them as needed within your functions. This way, you will be able to design your applications to align with user expectations and provide a seamless experience.

Now that you know how to handle multiple windows, you can continue building your Tkinter applications with confidence! If you have any questions or need further clarification, feel free to reach out or comment below.