GUI design using multiple notebooks

In this recipe, we will create our GUI using multiple notebooks. Surprisingly, tkinter does not ship out of the box with this functionality, but we can easily design such a widget.

Using multiple notebooks will further reduce the complexity discussed in the previous recipe.

Getting ready

We will create a new Python GUI similar to the one in the previous recipe. This time, however, we will design our GUI with two notebooks. In order to focus on this feature, we will use functions instead of class methods. 
Reading the previous recipe will be a good introduction to this recipe.

How to do it...

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