For fancy arrows you can play with the bbox
properties:
fig, ax = plt.subplots(1, 3, figsize=(7, 3))
pad_val = [-5, 0, 5]
for a,p in zip(ax, pad_val):
a.annotate('Here it is!\npad={}'.format(p),xy=(-1,-1),xytext=(1,1),
arrowprops=dict(arrowstyle='-|>', fc="k", ec="k", lw=1.5),
bbox=dict(pad=p, facecolor="none", edgecolor="none"))
a.set_xlim(-10,10)
a.set_ylim(-10,10)
Here the drawback is that you can't add a color behind the annotation (facecolor="none"
is mandatory), or the arrow will always stick to the border of the frame and it might be ugly.
HTH