import numpy as np
import matplotlib.pyplot as plt

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

x = np.arange(0, 10, 0.005)
y = np.exp(-x / 2.) * np.sin(2 * np.pi * x)

fig = plt.figure()

ax = fig.add_subplot(111)
ax.plot(x, y)

xy = ax.transData.transform([(0, 1), (1, 0)])\
    -ax.transData.transform((0, 0))

print("垂直长度：", xy[0][1])
print("水平长度： ", xy[1][0])

plt.show()

垂直长度： 269.5
水平长度： 581.25