When you add new fonts to your system, you need to delete your fontList.cache file in order for matplotlib to find them.
The file fontList.cache is located at your Userfolder –> .matplotlib/fontList.cache, for Windows that would normally be
# Create your ticker object with M ticks
M = 3
yticks = ticker.MaxNLocator(M)
# Set the yaxis major locator using your ticker object. You can also choose the minor
# tick positions with set_minor_locator.