How to force a thread to stop when the main program has been closed in Python

Last week, I had done with Tkinter GUI programming, and that program requires a lot of processing power to crawl and parse web pages. So, when I was running the program, it was hang. The solution is using multi-threading, but I found a next problem that threads were not killed when the main program was closed. To stop threads, we need to set daemon thread letting the threads die when the program is terminated.

Thread.setDaemon()