Drawing rectangle with border only in matplotlib

You just need to set the facecolor to the string ‘none’ (not the python None)

from matplotlib import pyplot as plt
from matplotlib.patches import Rectangle
someX, someY = 0.5, 0.5
fig,ax = plt.subplots()
currentAxis = plt.gca()
currentAxis.add_patch(Rectangle((someX - 0.1, someY - 0.1), 0.2, 0.2,
                      alpha=1, facecolor="none"))