threading.Thread() meet error

wxPython Users
#1

How to use threading.Thread() correct.
My code as follow, some time meet UI error.

def get_all_file_size(self, start_path):
    total = 0
    K, M, G = 1024, 1024**2, 1024**3
    MM = 100 * M # 100MB
    for path, dirs, files in os.walk(start_path):
        for f in files:
            fp = os.path.join(path, f)
            if os.path.isfile(fp):
                size = os.path.getsize(fp)
                total = total + 1
                if (size > MM):
                    self.text_multi_text.AppendText(fp + "  " +  str(float('%.2f' % (size/M))) + "M\n")

    self.text_multi_text.AppendText("\nTask is down, check files number: " + str(total))

def OnExecute(self, event):
    self.text_multi_text.Clear()
    self.text_multi_text.AppendText("More 100M file list\n")

    input = self.text_input.GetValue()
    # self.get_all_file_size(input)

    t1 = threading.Thread(target=self.get_all_file_size, args=(input,))
    t1.start()
#2

You should not call GUI code from outside your main thread.
See e.g. here: https://wiki.wxpython.org/LongRunningTasks or http://www.blog.pythonlibrary.org/2010/05/22/wxpython-and-threads/

So you can post events to the main thread which will then update things.

You may also do the update inside an EVT_IDLE handler. Often that’s fast enough.
Then use e.g. standard library collections.deque() to pass data to the main thread.
For controlling the worker thread you may use threading.Event.

Newbie: how do I start a Python process that runs in parallel to the GUI event loop?
#3

thanks very much
thanks very much

#4

Simply use CallAfter. Don’t bother trying anything else.

1 Like
#5

yes, wx.CallAfter work right. Thanks

def get_all_file_size(self, start_path):
    total = 0
    K, M, G = 1024, 1024**2, 1024**3
    MM = 100 * M # 100MB
    for path, dirs, files in os.walk(start_path):
        for f in files:
            fp = os.path.join(path, f)
            if os.path.isfile(fp):
                size = os.path.getsize(fp)
                total = total + 1
                if (size > MM):
                    # self.text_multi_text.AppendText(fp + "  " +  str(float('%.2f' % (size/M))) + "M\n")
                    wx.CallAfter(self.text_multi_text.AppendText, fp + "  " +  str(float('%.2f' % (size/M))) + "M\n")

    # self.text_multi_text.AppendText("\nTask is down, check files number: " + str(total))
    wx.CallAfter(self.text_multi_text.AppendText, "\nTask is down, check files number: " + str(total))
#6

I would also add that using pypubsub makes events management much easier (not only with threads).
A usage example is here.
Please note that wx.lib.pubsub is obsolete. Use pypubsub instead.

In a thread : CallAfter + sendMessage .
Something like this : wx.CallAfter(pub.sendMessage, "all_file_size", total=total)

1 Like
#7

good，the better

I’ll do some more learning assessment

#8

I like the hint of sending events down too, usually at abort, to care for a graceful exit… (may be difference of system folk & application guys :hot_face:)