Is there a way to send an event to wxApp? - multithreading

Question

I am using wxPython for the GUI, and I have a different thread that interacts with some I/O. Is there a way to update the GUI to show the I/O status when the thread receives an event from the I/O device?
To be clearer: every 3 seconds the IOthread asks to a parking bar if it is up or down, and I want the GUI to show a red led if it is down or a green led when it is up. So basically I need to communicate the information received by the IOthread to the GUI, which is running in the main thread

Answer 1

You could have a peek at pubsub but as you are using wxPython with a thread, it's easier to use a user defined event.
This adapted code, simply alternates between True and False, obviously you would change that and only post the event, if it changes.
from threading import Thread
import wx
import time
import wx.lib.newevent
progress_event, EVT_PROGRESS_EVENT = wx.lib.newevent.NewEvent()
class WorkThread(Thread):
def __init__(self,parent_target):
"""Init Worker Thread Class."""
Thread.__init__(self)
self.target = parent_target
self.stop_work_thread = 0
self.start() # start the thread
def run(self):
curr_loop = True
while True:
if self.stop_work_thread == 1: # Exit
break
time.sleep(1)
if self.stop_work_thread == 2: # Paused
continue
curr_loop = not curr_loop
evt = progress_event(active=curr_loop,name=self.name)
#Send back current bar position up True, Down False
try:
wx.PostEvent(self.target, evt)
except: # The parent frame has probably been destroyed
self.stop()
return
def stop(self):
self.stop_work_thread = 1
def pause(self):
if self.stop_work_thread == 2:
self.stop_work_thread = 0
self.target.pause_btn.SetLabel('Pause')
else:
self.stop_work_thread = 2
self.target.pause_btn.SetLabel('Paused')
class Progress(wx.Frame):
def __init__(self, parent, title):
super(Progress, self).__init__(parent, title = title,size = (500,300))
left_sizer = wx.BoxSizer(wx.VERTICAL)
middle_sizer = wx.BoxSizer(wx.HORIZONTAL)
self.panel = wx.Panel(self)
self.start_btn = wx.Button(self.panel, label="Start")
self.stop_btn =wx.Button(self.panel, label="Stop")
self.pause_btn =wx.Button(self.panel, label="Pause")
self.quit_btn =wx.Button(self.panel, label="Quit")
self.logger = wx.TextCtrl(self.panel, size=(200,200), style=wx.TE_MULTILINE | wx.TE_READONLY)
self.stop_btn.Disable()
self.pause_btn.Disable()
left_sizer.Add(self.start_btn,0,wx.EXPAND)
left_sizer.Add(self.stop_btn,0,wx.EXPAND)
left_sizer.Add(self.pause_btn,0,wx.EXPAND)
left_sizer.Add(self.quit_btn,0,wx.EXPAND)
middle_sizer.Add(self.logger,0,wx.EXPAND)
self.mainsizer = wx.BoxSizer(wx.HORIZONTAL)
self.mainsizer.Add(left_sizer)
self.mainsizer.Add(middle_sizer)
self.panel.SetSizer(self.mainsizer)
self.Layout()
self.start_btn.Bind(wx.EVT_BUTTON, self.onStart)
self.stop_btn.Bind(wx.EVT_BUTTON, self.onCancel)
self.pause_btn.Bind(wx.EVT_BUTTON, self.onPause)
self.quit_btn.Bind(wx.EVT_BUTTON, self.onExit)
#Bind to the progress event issued by the thread
self.Bind(EVT_PROGRESS_EVENT, self.OnActive)
self.Bind(wx.EVT_CLOSE, self.onExit)
def OnActive(self, event):
if not self.work.is_alive():
return
active = event.active
ident = event.name
if active:
self.logger.Clear()
self.logger.SetBackgroundColour("green")
self.logger.write('\n\n\n\n\n\t\tBar is Up')
else:
self.logger.Clear()
self.logger.SetBackgroundColour("red")
self.logger.write('\n\n\n\n\n\t\tBar is Down')
def onStart(self, event):
self.start_btn.Disable()
self.work = WorkThread(parent_target=self)
self.pause_btn.Enable()
self.stop_btn.Enable()
def onPause(self, event):
if self.work.is_alive():
self.work.pause() # Pause the thread
def onCancel(self, event):
"""Cancel thread process"""
try:
self.work.stop()
self.work.join()
except:
pass
self.onFinish()
def onFinish(self):
"""thread process finished - clean up"""
self.start_btn.Enable()
self.stop_btn.Disable()
self.pause_btn.Disable()
self.pause_btn.SetLabel("Pause")
self.logger.Clear()
self.logger.SetBackgroundColour("white")
def onExit(self, event):
self.onCancel(None)
self.onFinish()
self.Destroy()
app = wx.App()
frame = Progress(None,'Bar Up/Down Display')
frame.Show()
app.MainLoop()