When I call
self.client = ThreadedClient()
in my Python program, I get the error
"RuntimeError: main thread is not in main loop"
I have already done some googling, but I am making an error somehow ... Can someone please help me out?
Full error:
Exception in thread Thread-1:
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 530, in __bootstrap_inner
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 483, in run
File "/Users/Wim/Bird Swarm/bird_swarm.py", line 156, in workerGuiThread
self.root.after(200, self.workerGuiThread)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 501, in after
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1098, in _register
RuntimeError: main thread is not in main loop
Classes:
class ThreadedClient(object):
def __init__(self):
self.queue = Queue.Queue( )
self.gui = GuiPart(self.queue, self.endApplication)
self.root = self.gui.getRoot()
self.running = True
self.GuiThread = threading.Thread(target=self.workerGuiThread)
self.GuiThread.start()
def workerGuiThread(self):
while self.running:
self.root.after(200, self.workerGuiThread)
self.gui.processIncoming( )
def endApplication(self):
self.running = False
def tc_TekenVogel(self,vogel):
self.queue.put(vogel)
class GuiPart(object):
def __init__(self, queue, endCommand):
self.queue = queue
self.root = Tkinter.Tk()
Tkinter.Canvas(self.root,width=g_groottescherm,height=g_groottescherm).pack()
Tkinter.Button(self.root, text="Move 1 tick", command=self.doSomething).pack()
self.vogelcords = {} #register of bird and their corresponding coordinates
def getRoot(self):
return self.root
def doSomething():
pass #button action
def processIncoming(self):
while self.queue.qsize( ):
try:
msg = self.queue.get(0)
try:
vogel = msg
l = vogel.geeflocatie()
if self.vogelcords.has_key(vogel):
cirkel = self.vogelcords[vogel]
self.gcanvas.coords(cirkel,l.geefx()-g_groottevogel,l.geefy()-g_groottevogel,l.geefx()+g_groottevogel,l.geefy()+g_groottevogel)
else:
cirkel = self.gcanvas.create_oval(l.geefx()-g_groottevogel,l.geefy()-g_groottevogel,l.geefx()+g_groottevogel,l.geefy()+g_groottevogel,fill='red',outline='black',width=1)
self.vogelcords[vogel] = cirkel
self.gcanvas.update()
except:
print('Failed, was van het type %' % type(msg))
except Queue.Empty:
pass
You're running your main GUI loop in a thread besides the main thread. You cannot do this.
The docs mention offhandedly in a few places that Tkinter is not quite thread safe, but as far as I know, never quite come out and say that you can only talk to Tk from the main thread. The reason is that the truth is somewhat complicated. Tkinter itself is thread-safe, but it's hard to use in a multithreaded way. The closest to official documentation on this seems to be this page:
Q. Is there an alternative to Tkinter that is thread safe?
Tkinter?
Just run all UI code in the main thread, and let the writers write to a Queue object…
(The sample code given isn't great, but it's enough to figure out what they're suggesting and do things properly.)
There actually is a thread-safe alternative to Tkinter, mtTkinter. And its docs actually explain the situation pretty well:
Although Tkinter is technically thread-safe (assuming Tk is built with --enable-threads), practically speaking there are still problems when used in multithreaded Python applications. The problems stem from the fact that the _tkinter module attempts to gain control of the main thread via a polling technique when processing calls from other threads.
I believe this is exactly what you're seeing: your Tkinter code in Thread-1 is trying to peek into the main thread to find the main loop, and it's not there.
So, here are some options:
twisted
), it may have a way to integrate with Tkinter, in which case you should use that.mkTkinter
to solve the problem.Also, while I didn't find any exact duplicates of this question, there are a number of related questions on SO. See this question, this answer, and many more for more information.