Plot with an inset and a background color for the inset

plot_inset_rect.py

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches

x = np.linspace(0, 1, 100)
y = np.sin(4*np.pi*x)

# Big plot
ax = plt.subplot(111)
plt.plot(x, y, "k", zorder=3, alpha=0.4)
plt.xlabel("x")
plt.ylabel("y")
plt.ylim(-1, 5)
plt.grid()

# Rectangle
rec  = patches.Rectangle((0, 1), 0.8, 4, zorder=4, facecolor="#eeeeee")
ax.add_patch(rec)

# Small plot
ax2 = plt.axes([.25, .5, .4, .32], zorder=5)
plt.plot(x, y, "k", zorder=3, alpha=0.4)
plt.xlabel("x", fontsize=10)
plt.ylabel("y", fontsize=10)

plt.show()