Draw rectangular parallelepiped using the opposite vertices (diagonal)

plot_rectangular_parallelepiped.py

from mpl_toolkits.mplot3d import Axes3D
from mpl_toolkits.mplot3d.art3d import Poly3DCollection
import matplotlib.pyplot as plt

#    x  y  z
a = (1, 1, 1)  # p1
b = (2, 2, 2)  # p2

x, y, z = 0, 1, 2

vertices = [
    # XZ
    [(a[x], a[y], a[z]), (b[x], a[y], a[z]), (b[x], a[y], b[z]), (a[x], a[y], b[z])],
    [(a[x], b[y], a[z]), (b[x], b[y], a[z]), (b[x], b[y], b[z]), (a[x], b[y], b[z])],

    # YZ
    [(a[x], a[y], a[z]), (a[x], b[y], a[z]), (a[x], b[y], b[z]), (a[x], a[y], b[z])],
    [(b[x], a[y], a[z]), (b[x], b[y], a[z]), (b[x], b[y], b[z]), (b[x], a[y], b[z])],

    # XY
    [(a[x], a[y], a[z]), (b[x], a[y], a[z]), (b[x], b[y], a[z]), (a[x], b[y], a[z])],
    [(a[x], a[y], b[z]), (b[x], a[y], b[z]), (b[x], b[y], b[z]), (a[x], b[y], b[z])],
]

fig = plt.figure()

ax = fig.add_subplot(111, projection='3d')

ax.plot([a[x], b[x]], [a[y], b[y]], [a[z], b[z]], '-r')
ax.add_collection3d(Poly3DCollection(
    vertices, facecolors='cyan', linewidths=1, edgecolors='k', alpha=.2))

plt.show()