Fix font for Vietnamese plots in matplotlib python lib

untested.py

# I Used this with a IPython notebook using pandas, but I suppose that part isn't relevant
#
# Big thanks to guy who wrote this: http://www.himpactwxlab.com/home/how-to-wiki/change-matplotlib-fonts
#
# I had the problem that vietnamese characters showed as empty boxes. Although tones displayed properly.
# Here's the code to fix it:

import matplotlib
import matplotlib.font_manager as font_manager

sorted(font_manager.findSystemFonts())  # Print this to see available fonts

fontpath = '/usr/share/fonts/truetype/freefont/FreeSans.ttf'
# Naturally I picked the font with the most "GNU-ish" name, assuming it has good i18n
# (assumption turned out to be correct :D)

prop = font_manager.FontProperties(fname=fontpath)
matplotlib.rcParams['font.family'] = prop.get_name()

# Done, now you can use it, like:
my_pandas_dataframe.plot(kind='bar')