In a python program I am writing, I get an error saying Traceback (most recent call last): File "/Applications/Canopy.app/appdata/canopy-1.4.0.1938.macosx- x86_64/Canopy.app/Contents/lib/python2.7/lib-tk/Tkinter.py", line 1470, in __call__ return self.func(*args) File "/Users/lkloh/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/backends/backend_tkagg.py", line 413, in button_release_event FigureCanvasBase.button_release_event(self, x, y, num, guiEvent=event) File "/Users/lkloh/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/backend_bases.py", line 1808, in button_release_event self.callbacks.process(s, event) File "/Users/lkloh/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/cbook.py", line 525, in process del self.callbacks[s][cid] KeyError: 103 Do you have any idea how I can debug this/ what could be wrong? The error message does not point to anywhere in code I have personally written. I get the error message only after I close my GUI window, but I want to fix it even though it does not break the functionality of my code. The error is part of a very big program I am writing, so I cannot post all my code, but below is code I think is relevant: def save(self, event): self.getSaveAxes() self.save_connect() def getSaveAxes(self): saveFigure = figure(figsize=(8,1)) saveFigure.clf() # size of save buttons rect_saveHeaders = [0.04,0.2,0.2,0.6] rect_saveHeadersFilterParams = [0.28,0.2,0.2,0.6] rect_saveHeadersOverride = [0.52,0.2,0.2,0.6] rect_saveQuit = [0.76,0.2,0.2,0.6] #initalize axes saveAxs = {} saveAxs['saveHeaders'] = saveFigure.add_axes(rect_saveHeaders) saveAxs['saveHeadersFilterParams'] = saveFigure.add_axes(rect_saveHeadersFilterParams) saveAxs['saveHeadersOverride'] = saveFigure.add_axes(rect_saveHeadersOverride) saveAxs['saveQuit'] = saveFigure.add_axes(rect_saveQuit) self.saveAxs = saveAxs self.save_connect() self.saveFigure = saveFigure show() def save_connect(self): #set buttons self.bn_saveHeaders = Button(self.saveAxs['saveHeaders'], 'Save\nHeaders\nOnly') self.bn_saveHeadersFilterParams = Button(self.saveAxs['saveHeadersFilterParams'], 'Save Headers &\n Filter Parameters') self.bn_saveHeadersOverride = Button(self.saveAxs['saveHeadersOverride'], 'Save Headers &\nOverride Data') self.bn_saveQuit = Button(self.saveAxs['saveQuit'], 'Quit') #connect buttons to functions they trigger self.cid_saveHeaders = self.bn_saveHeaders.on_clicked(self.save_headers) self.cid_savedHeadersFilterParams = self.bn_saveHeadersFilterParams.on_clicked(self.save_headers_filterParams) self.cid_saveHeadersOverride = self.bn_saveHeadersOverride.on_clicked(self.save_headers_override) self.cid_saveQuit = self.bn_saveQuit.on_clicked(self.save_quit) def save_quit(self, event): self.save_disconnect() close()