vertical & horizontal lines in matplotlib

Question

I do not quite understand why I am unable to create horizontal and vertical lines at specified limits. I would like to bound the data by this box. However, the sides do not

Answer 1

If you want to add a bounding box, use a rectangle:

ax = plt.gca()
r = matplotlib.patches.Rectangle((.5, .5), .25, .1, fill=False)
ax.add_artist(r)

Rectangle doc