Implementing my own event loop in a wxPython application

Question

I’m writing a wxPython application that will be doing quite a bit of data analysis and display. The way I’ve written it so far has led to problems when two threads try to change

Answer 1

You can use wx.callafter, it takes a callable object that is called in the guis mainloop after the current and pending event handlers have been completed. Any extra positional or keyword args are passed on to the callable when it is called.

Here is an example of gui code that takes advantage of wx.CallAfter when running a separate thread and updating the GUI in the main thread.

The code is by Andrea Gavana which is found in the wxpython Phoenix docs

#!/usr/bin/env python

# This sample shows how to take advantage of wx.CallAfter when running a
# separate thread and updating the GUI in the main thread

import wx
import threading
import time

class MainFrame(wx.Frame):

    def __init__(self, parent):
        wx.Frame.__init__(self, parent, title='CallAfter example')

        panel = wx.Panel(self)
        self.label = wx.StaticText(panel, label="Ready")
        self.btn = wx.Button(panel, label="Start")
        self.gauge = wx.Gauge(panel)

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.label, proportion=1, flag=wx.EXPAND)
        sizer.Add(self.btn, proportion=0, flag=wx.EXPAND)
        sizer.Add(self.gauge, proportion=0, flag=wx.EXPAND)

        panel.SetSizerAndFit(sizer)
        self.Bind(wx.EVT_BUTTON, self.OnButton)

    def OnButton(self, event):
        """ This event handler starts the separate thread. """
        self.btn.Enable(False)
        self.gauge.SetValue(0)
        self.label.SetLabel("Running")

        thread = threading.Thread(target=self.LongRunning)
        thread.start()

    def OnLongRunDone(self):
        self.gauge.SetValue(100)
        self.label.SetLabel("Done")
        self.btn.Enable(True)

    def LongRunning(self):
        """This runs in a different thread.  Sleep is used to
         simulate a long running task."""
        time.sleep(3)
        wx.CallAfter(self.gauge.SetValue, 20)
        time.sleep(5)
        wx.CallAfter(self.gauge.SetValue, 70)
        time.sleep(4)
        wx.CallAfter(self.OnLongRunDone)

if __name__ == "__main__":
    app = wx.App(0)
    frame = MainFrame(None)
    frame.Show()
    app.MainLoop()