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POBeginner-level Python threading problems
 

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    <p>As someone new to GUI development in Python (with pyGTK), I've just started learning about threading. To test out my skills, I've written a simple little GTK interface with a start/stop button. The goal is that when it is clicked, a thread starts that quickly increments a number in the text box, while keeping the GUI responsive.</p> <p>I've got the GUI working just fine, but am having problems with the threading. It is probably a simple problem, but my mind is about fried for the day. Below I have pasted first the trackback from the Python interpreter, followed by the code. You can go to <a href="http://drop.io/pxgr5id" rel="noreferrer">http://drop.io/pxgr5id</a> to download it. I'm using bzr for revision control, so if you want to make a modification and re-drop it, please commit the changes. I'm also pasting the code at <a href="http://dpaste.com/113388/" rel="noreferrer">http://dpaste.com/113388/</a> because it can have line numbers, and this markdown stuff is giving me a headache.</p> <p>Update 27 January, 15:52 EST: Slightly updated code can be found here: <a href="http://drop.io/threagui/asset/thread-gui-rev3-tar-gz" rel="noreferrer">http://drop.io/threagui/asset/thread-gui-rev3-tar-gz</a></p> <p><strong>Traceback</strong></p> <pre><code>crashsystems@crashsystems-laptop:~/Desktop/thread-gui$ python threadgui.pybtnStartStop clicked Traceback (most recent call last): File "threadgui.py", line 39, in on_btnStartStop_clicked self.thread.stop() File "threadgui.py", line 20, in stop self.join() File "/usr/lib/python2.5/threading.py", line 583, in join raise RuntimeError("cannot join thread before it is started") RuntimeError: cannot join thread before it is started btnStartStop clicked threadStop = 1 btnStartStop clicked threadStop = 0 btnStartStop clicked Traceback (most recent call last): File "threadgui.py", line 36, in on_btnStartStop_clicked self.thread.start() File "/usr/lib/python2.5/threading.py", line 434, in start raise RuntimeError("thread already started") RuntimeError: thread already started btnExit clicked exit() called </code></pre> <p><strong>Code</strong></p> <pre><code>#!/usr/bin/bash import gtk, threading class ThreadLooper (threading.Thread): def __init__ (self, sleep_interval, function, args=[], kwargs={}): threading.Thread.__init__(self) self.sleep_interval = sleep_interval self.function = function self.args = args self.kwargs = kwargs self.finished = threading.Event() def stop (self): self.finished.set() self.join() def run (self): while not self.finished.isSet(): self.finished.wait(self.sleep_interval) self.function(*self.args, **self.kwargs) class ThreadGUI: # Define signals def on_btnStartStop_clicked(self, widget, data=None): print "btnStartStop clicked" if(self.threadStop == 0): self.threadStop = 1 self.thread.start() else: self.threadStop = 0 self.thread.stop() print "threadStop = " + str(self.threadStop) def on_btnMessageBox_clicked(self, widget, data=None): print "btnMessageBox clicked" self.lblMessage.set_text("This is a message!") self.msgBox.show() def on_btnExit_clicked(self, widget, data=None): print "btnExit clicked" self.exit() def on_btnOk_clicked(self, widget, data=None): print "btnOk clicked" self.msgBox.hide() def on_mainWindow_destroy(self, widget, data=None): print "mainWindow destroyed!" self.exit() def exit(self): print "exit() called" self.threadStop = 1 gtk.main_quit() def threadLoop(self): # This will run in a thread self.txtThreadView.set_text(str(self.threadCount)) print "hello world" self.threadCount += 1 def __init__(self): # Connect to the xml GUI file builder = gtk.Builder() builder.add_from_file("threadgui.xml") # Connect to GUI widgets self.mainWindow = builder.get_object("mainWindow") self.txtThreadView = builder.get_object("txtThreadView") self.btnStartStop = builder.get_object("btnStartStop") self.msgBox = builder.get_object("msgBox") self.btnMessageBox = builder.get_object("btnMessageBox") self.btnExit = builder.get_object("btnExit") self.lblMessage = builder.get_object("lblMessage") self.btnOk = builder.get_object("btnOk") # Connect the signals builder.connect_signals(self) # This global will be used for signaling the thread to stop. self.threadStop = 1 # The thread self.thread = ThreadLooper(0.1, self.threadLoop, (1,0,-1)) self.threadCounter = 0 if __name__ == "__main__": # Start GUI instance GUI = ThreadGUI() GUI.mainWindow.show() gtk.main() </code></pre>
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