I have already read
http://wiki.wxpython.org/LongRunningTasks
http://wiki.wxpython.org/CallAfter
and searched a lot in Google but found no answer to my problem. Because in my opinion it would be to much code and it is more a theoretical problem, I hope it is ok without code.
What I want to do with an example: I have a grid (wx.grid) with check boxes in the main thread. Then I start a new thread (thread.start_new_thread) where I go through all rows (1 second per row) and check if the checkbox is set. If it is set, some job is done.
This is working, if I read out all rows before I start the thread. But I need to read it out while the thread is running, because the user should have the ability to uncheck or check another checkbox! But if I read it out in the new thread sometimes a “NonType Object is not callable” error is raised. I think because wx.CallAfter should be used to interact with the grid in the other thread. But CallAfter I can not use to get the return value.
I have no idea how to solve this issue. Perhaps some people with more thread experience have some idea? If you need additional data please ask, but I think that my example contains all necessary information.
A common approach to this type of thing is to use a Queue.Queue object to pass commands to one or more worker threads. The worker thread(s) will wait on a pull from the queue until there are items in the queue ready to be pulled. Part of the command object could be a target in the GUI thread to send a message to (in a thread-safe way, like with wx.CallAfter) when the command is completed.
You should also take a look at the wx.lib.delayedresult module. It is similar to the above but a little more capable and robust.