wxpython threading textctrl delay

Question

I have any issue with wxpython's textctrl and threading. Would appreciate any help in resolving this issue.

My program processes files, as and when each file is processed it is listed within the textctrl as being completed. When working with just a few files the textctrl is responsive and displays itself immediately and does not disappear. Even if these files are large. Did a test on a 700mb file and textctrl worked perfectly.

The problem occurs when workin on many files, say 20+ for exmaple. Under these circumstances the textctrl disappears for 6 or 7 seconds, then reappears and works as normal.

I have tried normal threading, daemon threading etc.. Also tried using .join() which made things even worse. I'm wondering if this is just because my program is very processor intensive, or if I'm just doing something wrong.

My thread line of code is listed below. So far this is by far the fastest method, just not good enough for my purposes. Thanks in advance, Clinton.

def Worker(self, e, _file):

    match = ''

    with open(_file, 'r') as f:
        data = f.read()

    for char in data:
        if char in self.key:
            match += chr(self.key.index(char))

    open(_file, 'w').close()

    with open(_file, 'w') as f:
        f.write(match)

    wx.CallAfter(self.ListFilesEncrypt, e, _file)

if __name__ == '__main__':
    for _file in self.file2process:
        self.filenum += 1
        Thread(target=self.Worker, args=(e, _file,)).start()

Answer 1

Update the GUI using thread-safe methods. In wxPython, there are 3:

• wx.CallAfter
• wx.CallLater
• wx.PostEvent

You should also take a look the wxPython wiki for information on wxPython and threading:

• http://wiki.wxpython.org/LongRunningTasks

I also wrote a tutorial on the topic:

• http://www.blog.pythonlibrary.org/2010/05/22/wxpython-and-threads/

UPDATE: Here is a simple example that creates 40 threads and "processes" 40 made up files. It updates the display when each thread is done. However, I do not see the issue you speak of.

import random
import time
import wx

from threading import Thread
from wx.lib.pubsub import Publisher

########################################################################
class TestThread(Thread):
    """Test Worker Thread Class."""

    #----------------------------------------------------------------------
    def __init__(self, fname, sleepAmt):
        """Init Worker Thread Class."""
        Thread.__init__(self)
        self.fname = fname
        self.sleepAmt = sleepAmt
        self.start()    # start the thread

    #----------------------------------------------------------------------
    def run(self):
        """Run Worker Thread."""
        # This is the code executing in the new thread.
        time.sleep(self.sleepAmt)
        msg = "%s finished in %s seconds!" % (self.fname, self.sleepAmt)
        wx.CallAfter(Publisher().sendMessage, "update", msg)


########################################################################
class MyForm(wx.Frame):

    #----------------------------------------------------------------------
    def __init__(self):
        wx.Frame.__init__(self, None, wx.ID_ANY, "Tutorial")

        panel = wx.Panel(self, wx.ID_ANY)
        self.updateText = wx.TextCtrl(panel, style=wx.TE_MULTILINE)
        self.btn = btn = wx.Button(panel, label="Start Thread")

        btn.Bind(wx.EVT_BUTTON, self.onButton)

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.updateText, 1, wx.ALL|wx.EXPAND, 5)
        sizer.Add(btn, 0, wx.ALL|wx.CENTER, 5)
        panel.SetSizer(sizer)

        # create a pubsub receiver
        Publisher().subscribe(self.updateDisplay, "update")

    #----------------------------------------------------------------------
    def onButton(self, event):
        """
        Runs the thread
        """
        for i in range(40):
            fname = "test%s.txt" % i
            secs = random.choice(range(3, 15))
            TestThread(fname, secs)

    #----------------------------------------------------------------------
    def updateDisplay(self, msg):
        """
        Receives data from thread and updates the display
        """
        data = msg.data + "\n"
        self.updateText.WriteText(data)

#----------------------------------------------------------------------
# Run the program
if __name__ == "__main__":
    app = wx.PySimpleApp()
    frame = MyForm().Show()
    app.MainLoop()

I am running on Windows 7 using Python 2.6 with wxPython 2.8.12.1

Answer 2

Your threads should not update the text control directly - they should either use wx.CallAfter or, better, set a flag for the main, (GIU), thread to update the control - it sounds like a on end thread method might be appropriate.

Answer 3

More than CPU-intensive, it can be IO-intensive. And IO-intensive applications can have a very big impact on performance, especially when you are also using the IO-units for other critical purposes like paging. I'd suggest to serve 5 to 10 at a time and queue the rest.

Answer 4

I am using wxpython 4.1.1 and have found that this no longer works.

wxPyDeprecationWarning: wx.lib.pubsub has been deprecated, plese migrate your code to use pypubsub, available on PyPI.
======================================================================
          ***    ATTENTION   ***
This messaging protocol is deprecated. This module, and hence arg1
messaging protocol, will be removed in v3.4 of PyPubSub. Please make
the necessary changes to your code so that it no longer requires this
module. The pypubsub documentation provides steps that may be useful
to minimize the chance of introducing bugs in your application.
======================================================================