Strange threading behaviour

[Rotwang]

Hi all, I'm using Python 2.7.2 on Windows 7 and a module I've written is 
acting strangely. I can reproduce the behaviour in question with the 
following:

--- begin bugtest.py ---

import threading, Tkinter, os, pickle

class savethread(threading.Thread):
     def __init__(self, value):
         threading.Thread.__init__(self)
         self.value = value
     def run(self):
         print 'Saving:',
         with open(os.path.join(os.getcwd(), 'bugfile'), 'wb') as f:
             pickle.dump(self.value, f)
         print 'saved'

class myclass(object):
     def gui(self):
         root = Tkinter.Tk()
         root.grid()
         def save(event):
             savethread(self).start()
         root.bind('s', save)
         root.wait_window()

m = myclass()
m.gui()

--- end bugtest.py ---


Here's the problem: suppose I fire up Python and type

 >>> import bugtest

and then click on the Tk window that spawns and press 's'. Then 
'Saving:' gets printed, and an empty file named 'bugfile' appears in my 
current working directory. But nothing else happens until I close the Tk 
window; as soon as I do so the file is written to and 'saved' gets 
printed. If I subsequently type

 >>> bugtest.m.gui()

and then click on the resulting window and press 's', then 'Saving: 
saved' gets printed and the file is written to immediately, exactly as I 
would expect. Similarly if I remove the call to m.gui from the module 
and just call it myself after importing then it all works fine. But it 
seems as if calling the gui within the module itself somehow stops 
savethread(self).run from finishing its job while the gui is still alive.

Can anyone help?


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