Thanks for pointing out this drawing arrow patch.
I wrote a quick function to use this.
Figuring out the correct width to use requires some experimentation.
It would be nice if we could eventually have a line with a regular
line width, and a nicely sized arrow head. (Any ideas?).
But this gives nices results.
from pylab import *
def draw_arrow( x, y, dx, dy, width=1, color = 'k' ):
ax = gca()
a = Arrow( x, y, dx, dy, width )
ax.add_patch( a )