ec_fill_between_gca.py

import numpy as np

linear_data = np.array([1,2,3,4,5,6,7,8])
exponential_data = linear_data**2

plt.figure()
plt.plot(linear_data, '-o', exponential_data, '-o')

# fill the area between the linear data and exponential data
plt.gca().fill_between(range(len(linear_data)), 
                       linear_data, exponential_data, 
                       facecolor='blue', 
                       alpha=0.25)

plt.legend(['Baseline', 'Competition'])