A high-tech solution would be to use matplotlib in Tkinter. It provides a smaller version Latexthat it calls mathtext . This route does not look easy, but it seems possible. See this for more details . If this method seems too involved, a similar, but perhaps simpler idea is to use MathML (officially part of HTML5) for markup. Tkinter may be easier to embed.
A relatively low-tech approach would be to use two labels (with invisible borders) for the numerator and denominator, respectively, with a thin rectangle between them. This will require some tweaking, but you should be able to tweak the fonts and alignment so that the result looks like a single expression.