How to set a Matplotlib rectangle edge to outside of specified width?

To set a Matplotlib rectangle edge to outside of specified width, we can take the following steps −

• Set the figure size and adjust the padding between and around the subplots.
• Create a new figure or activate an existing figure.
• Add an ax to the figure as part of a subplot arrangement.
• Initialize a variable line_width to set the rectangle outside of specified width. Use the variables xy, w and h for rectangle's center, width and height.
• Get a rectangle instance, with xy anchor points and its height and width.
• Get the offset transformbox instance.
• Add an artist patch, r (Step 5).
• Get the container for an OffsetBox instance.
• Add an annotation box, ab, to the container box.
• To display the figure, use show() method.

Example

import matplotlib.pyplot as plt
from matplotlib.patches import Rectangle
from matplotlib.offsetbox import AnnotationBbox, AuxTransformBox

plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

fig = plt.figure()

ax = fig.add_subplot(111)
ax.plot([1, 6, 8, 6])

line_width = 7
xy, w, h = (1, 3), 2, 2
r = Rectangle(xy, w, h, fc='green', ec='orange', lw=3)

offsetbox = AuxTransformBox(ax.transData)
offsetbox.add_artist(r)

ab = AnnotationBbox(offsetbox, (xy[0] + w /, xy[1] + w /),
   boxcoords="data", pad=0.52, fontsize=line_width,
   bboxprops=dict(facecolor="none", edgecolor='r',
   lw=line_width))
ax.add_artist(ab)

plt.show()

Output