How to clear window with tkinter

The simplest thing is to have your function create a single frame, and then place all of the widgets in that frame. The frame can then be placed in the main window such that it fills the whole window. Then, to delete everything you simply need to delete that one frame.

Another way to "move on to the next screen" is to use this same method, but create all of the frames ahead of time. You can stack these frames on top of each other, and use lift and/or lower to determine which one is on top. The one on top will obscure the ones below.

For an example of stacking, see Switch between two frames in tkinter

As for the problem of frame2 not knowing how to destroy frame1, you simply need to pass in a reference to the existing frame when creating a new frame, or pass in a reference to a "controller" - a function that knows about all the frames. You then ask the controller to delete the current frame, and the controller will know what the current frame is.

A button calling a function that deletes all existing frames and rebuilds another sounds like a design flaw. The propensity for errors (forgetting to delete certain elements in some places of the code etc) is pretty large.

If you don't have an insane number of UI elements, I suggest creating them all at once, and hiding/showing various elements as necessary.

Take a look at this SO answer for how you might go about creating GUI elements that can be shown/hidden, and how the callback function might look.

Edit: If you really need to do it based on these functions, then I guess an alternative approach might be this:

Say 'top_frame' is the frame that includes all your widgets which you want to destroy when you run function #2. Change all of your GUI elements in function #1 so that when you create them, you explicitly pass them top_frame so that they have a link to it (self.top_frame = top_frame). This means your button will also have an attribute self.top_frame. You pass that as one of the arguments to function #2, and function #2 now can refer to top_frame and destroy it.

But definitely prone to error and probably slower due to all the creation/destruction of GUI elements. I recommend going through the code in the answer above when you have the time, it really is a much better solution.