How does python write interface programs?

After reading your question, several answers don’t seem to be completely correct. Let me add something to you.

Your problem basically has nothing to do with flask. Flask is a simple micro-programming framework that is beautiful, easy to use and easy to use. However, it only implements the server-side interaction part based on the HTTP protocol.

In addition to server-side interaction, an interface design also requires local interaction (implemented with JS, flash), and the most important thing is a client interface (implemented with HTML CSS JS). File upload requirements (JQUERY UPLOADFILE library)

From the above answer, it seems that you have just started to do this. I suggest you follow this line of thinking.

Learn html2.0 first, not 4.01, nor 5.0, because 2.0 is more basic. Then use frame and table to make your interface. First implement the left part

Then learn css and complete the two buttons on your left. You can also use TABLE, such as stupid. Then use CSS to change the frame method into an iframe implementation

Use the traditional HTML method to implement the upload and download on the right

Learn jquery and use the uploadfile function to re-implement the upload function on the right

If you learn quickly, it will take 1 week. If you learn slowly, it is uncertain, maybe 3 weeks to complete.