Multithreading tkinter question

Mark English Mark.English at liffe.com
Wed Dec 15 19:21:48 CET 2004


Is there a safe way to run tkinter in a multithreaded app where the
mainloop runs in a background thread ?
Here's some test code demonstrating the problem. I'm running Python2.4
under Windows 2000.


----------------Code snip starts-------------
from Tkinter import *

def GetTkinterThread():
    import threading
    def TestTkinter():
        def greeting():
            print "Hello stdout world !"

        win = Frame()
        win.pack()
        Label(win, text="Hello container world").pack(side=TOP)
        Button(win, text="Hello", command=greeting).pack(side=TOP)
        Button(win, text="Quit", command=win.quit).pack(side=RIGHT)

        win.mainloop()
    #Run the mainloop in another thread
    t = threading.Thread(None, TestTkinter, 'Test Tkinter Thread')
    t.setDaemon(1)   #Keep going
    t.start()
    print 'Hi'
    return t

t = GetTkinterThread() #This works fine

#Now press the "Hello" button on the Tkinter window
#Now press the return key at the python prompt

----------------Code snip ends-------------
With a debug build the call stack looks like this:
 	python24_d.dll!Py_FatalError(const char * msg=0x1e23ca14)  Line
1513	C
 	python24_d.dll!PyThreadState_Swap(_ts * new=0x0098d0b8)  Line
293 + 0xa	C
 	python24_d.dll!PyEval_RestoreThread(_ts * tstate=0x0098d0b8)
Line 309 + 0x9	C
 	_tkinter_d.pyd!EventHook()  Line 2969 + 0xc	C
 	python24_d.dll!my_fgets(char * buf=0x009ef3e8, int len=100,
_iobuf * fp=0x1027c838)  Line 46	C
 	python24_d.dll!PyOS_StdioReadline(_iobuf * sys_stdin=0x1027c838,
_iobuf * sys_stdout=0x1027c858, char * prompt=0x0087f974)  Line 125 +
0x11	C
	python24_d.dll!PyOS_Readline(_iobuf * sys_stdin=0x1027c838,
_iobuf * sys_stdout=0x1027c858, char * prompt=0x0087f974)  Line 205 +
0x12	C

Is this because of access to sys.stdout ? Or some deeper darker problem
? Is there a right way to achieve this ? Basically I want to be able to
call a function from the Python prompt which creates a Tkinter window
(not necessarily interactive apart from a close button) to display some
data, but leaves the Python prompt active so I can carry on from there.

Haven't found anything about this yet. All sample multithreaded Tkinter
code I've seen uses the main thread as the GUI thread. Also, should I be
posting this to another newsgroup ?

Thanks for any help,
Mark


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