Binding confusion in Tkinter

Hello, everyone :-)

And now for something completely different: I am experiencing a slight problem with binding to Shift-Return key event in Tkinter.

I am writing a front end to Python a la Mathematica's so that I might be able to display non-ASCII characters, save the contents of the window in a file etc.

I created a Text widget, in which I type the command, then press the "CALCULATE" button and the result appears on the next line. I would like to bind the action performed by the "CALCULATE" button to a sequence of keys Shift-Return, again, just as in Mathematica. This binding works (that is, calculation is done and the result is displayed after Shift-Return has been pressed), but together with a direct action of Shift-Return on text (that is, the cursor jumps to the next line).

Here's the piece of my code where the problem occurs (resides in the __init__ method):

b=Button(toolbar,text="CALCULATE",command=lambda s=self:s.calculate_bttn(text))
text.bind("<Shift-Return>",lambda event:self.calculate_bttn(text))

where "calculate_bttn(self,widget)" is a method defined in the current class.

Note that if I bind to text (just as shown above), the calculation (according to calculate_bttn(self,widget)) is performed first, and after that the line (due to Shift-Return action) is inserted. But if I bind to master (the main window), the sequence of events is reverse: first the line is inserted and then calculate_bttn(self,widget) runs.

Does anybody have any idea how to stifle the unneeded, unbinded action of Shift-Return, which makes the cursor jump to the next line?

I understand that I am probably binding to two different widgets, but I can't perceive how to solve the problem descpite already spending three hours on it.

Any help will be greatly appreciated.

Thank you.

Arteum

According to The Tkinter reference your event handler should return a "break" string to break the chain of handlers:



This should swallow the Shift-Return characters.

Grim