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Multi-Threaded Work - Running long tasks inside of a GUI
This program demonstrates one way of using a combination of Python's Thread and Queue objects to implement a GUI that performs work that takes too long to directly perform inside of the event loop.
An example use would be if you have a button that you want to use to start some code that will take several seconds to run, then this technique is a good pattern to use.
Take a moment to examine the code dealing with the Thread and the Queue. These constructs are nothing to fear as the amount of code that uses them is only a handul of lines of code are needed. And they are simple enough that you'll be able to understand them.
"Thread-safe" - This is an important term to consider any time you are using threads in your program. There are 2 things to check out:
- You must make sure that the calls you make from your thread are OK to call from a thread
- If you are running multiple threads, then the calls you make must be "thread-safe"
The authors of libraries you are using often tell you if their code is "thread-safe".
PySimpleGUI code is not thread safe. For the tkinter version (i.e. plain PySimpleGUI versus PySimpleGUIQt), you cannot run PySimpleGUI as a thread. To put that in simpler terms, you cannot make any calls into the PySimpleGUI package from a thread. For example, you cannot call update for any of your elements from a thread. This is why you see the updates happening from the main thread only.
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