.rc solution given changes the default font for all drawing.
Here is a solution for doing this when you don't want to change all the fonts, but just the font properties of the legend of this particular graph (a legend belonging to a particular
L = ax.legend() plt.setp(L.texts, family='Consolas')
This allows you to choose a different font for the legend and the axes. I found this helpful when I needed a monospace font for my legend, but not for the axes -- allowing me to create a neat legend like this:
Note how the title is a different font than the legend - this gives me an alignment of numbers that would otherwise be hard to achieve.