Secondary Tkinter window won&#39;t open until script finished running
Tags: python, tkinter
Published: 2023-08-21 17:06:00

Have you ever encountered a situation where you tried to open a secondary window in Tkinter, but it just wouldn't appear until your script finished running? It can be frustrating, especially when you're eager to see the results of your hard work. But fear not, because we're here to help you understand why this happens and how to fix it!

First, let's understand why this issue occurs. Tkinter, the popular Python GUI toolkit, is based on the Tcl/Tk framework. When you create a Tkinter window, it runs in a single thread. This means that any time-consuming tasks, such as lengthy calculations or network requests, will block the main thread and prevent the secondary window from being displayed until the script finishes executing.

Now, you might be wondering, why doesn't Tkinter open the secondary window first and then continue executing the script? Well, the reason is that Tkinter follows a sequential execution model. It executes your code line by line, and until it reaches the point where it creates the secondary window, it won't display anything on the screen.

So, how can we solve this problem? One solution is to use threading. By moving the time-consuming tasks to a separate thread, we can prevent them from blocking the main thread and allow the secondary window to open immediately. Here's an example:

`import tkinter as tk import threading def time\_consuming\_task(): # Perform time-consuming calculations here def open\_secondary\_window(): secondary\_window = tk.Toplevel(root) # Configure and display the secondary window # Create the main window root = tk.Tk() # Create a button to open the secondary window button = tk.Button(root, text="Open Secondary Window", command=open\_secondary\_window) button.pack() # Create a thread for the time-consuming task task\_thread = threading.Thread(target=time\_consuming\_task) # Start the thread task_thread.start() # Start the Tkinter event loop root.mainloop()`

By using threading, we can execute the time-consuming task in the background while the main thread continues running, allowing the secondary window to open immediately. This way, you can enjoy the benefits of multi-threading and have a responsive user interface.

Remember, though, with great power comes great responsibility. Threading can introduce its own set of challenges, such as race conditions and synchronization issues. So, make sure to handle thread safety properly and use the appropriate synchronization mechanisms when necessary.

Now that you know how to solve the issue of the secondary Tkinter window not opening until the script finishes running, you can create more interactive and responsive GUI applications. Happy coding!

**References:**

*   Python Software Foundation. (n.d.). Tkinter — Python interface to Tcl/Tk. _Python 3.9.7 documentation_. Retrieved from [https://docs.python.org/3/library/tkinter.html](https://docs.python.org/3/library/tkinter.html)
*   Geek University. (2021). _Python GUI Programming With Tkinter_. Retrieved from [https://geek-university.com/python/python-gui-programming-with-tkinter/](https://geek-university.com/python/python-gui-programming-with-tkinter/)