Threading in wxpython - python-2.7

Question

Hi I'm new to python and have started developing a GUI using wxpython. I just want to know the basic threading operation in wxpython. I have a main process which has OK & Cancel Buttons and a child process derived from main with the OK and Cancel Buttons. I want to implement threading such a way that clicking OK button on main process must send a message to child process and child process must look for if any of it's process is running, if so, it has to wait for that process to finish and then receive the message from main process.Similarly the same with the Cancel button in the main process.
Basically i want to see how child process receives message from main process and both work parallel.
I'm trying with wx.CallAfter and wx.PostEvent and i'm confused with the threading concept here. Please someone help me.
Thanks in advance

Answer 1

Multithreading in wxpython is not different than in python. wx.CallAfter and threading example shows how you use both. wx.CallAfter waits for the event to be completed and run the handler in the main thread. Additionally, you can use timers (wx.Timer) to check child processes and send/receive data.
Here is a link for wx.PostEvent showing how to use it. In this example, you create custom event, bind it to a handler in main thread. After that you post the event in a worker thread and attach some data as well. Your event handler receives the event and do some stuff in the main thread.
So, there are important questions arising when you use multithreading
When to start the child threads,
Which communication mechanism is used between threads,
How to stop the threads in a safe way when necessary,
etc.
I would prefer wx.Timer + Queue module. I can regularly check the queue with timers or with user events and send something (i.e. None) through queue to stop threads.
Note: Long running jobs in main thread can make GUI unresponsive.

Answer 2

I got it right. THanks to #ozy
import threading
import wx
from threading import Thread
ID_RUN = 101
ID_RUN2 = 102
class ChildThread(Thread):
def __init__(self, myframe):
"""Init Worker Thread Class."""
Thread.__init__(self)
self.myframe = myframe
def run(self):
wx.CallAfter(self.myframe.AfterRun, 'Ok button pressed')
class MyFrame(wx.Frame):
def __init__(self, parent, ID, title):
wx.Frame.__init__(self, parent, ID, title)
panel = wx.Panel(self, -1)
mainSizer = wx.BoxSizer(wx.HORIZONTAL)
mainSizer.Add(wx.Button(panel, ID_RUN, "OK"))
mainSizer.Add(wx.Button(panel, ID_RUN2, "Cancel"))
panel.SetSizer(mainSizer)
mainSizer.Fit(self)
wx.EVT_BUTTON(self, ID_RUN, self.onRun)
wx.EVT_BUTTON(self, ID_RUN2, self.onRun2)
def onRun(self, event):
self.child = ChildThread(myframe=self)
self.child.daemon = True
self.child.start()
def onRun2(self, event):
self.child2 = threading.Thread(None, self.__run)
self.child2.daemon = True
self.child2.start()
def __run(self):
wx.CallAfter(self.AfterRun, "Cancel button pressed")
def AfterRun(self, msg):
dlg = wx.MessageDialog(self, msg, "Message", wx.OK | wx.ICON_INFORMATION)
dlg.ShowModal()
dlg.Destroy()
class MyApp(wx.App):
def OnInit(self):
frame = MyFrame(None, -1, "My GUI")
frame.Show(True)
frame.Centre()
return True
app = MyApp(0)
app.MainLoop()