xxxxxxxxxx
x=data_price['month']
y = data_price['price_off_peak_var']
y1 = data_price['price_peak_var']
y2 = data_price['price_mid_peak_var']
fig, ax = plt.subplots()
ax.plot(x, y)
ax.plot(x, y1)
plt.show()
xxxxxxxxxx
import matplotlib.pyplot as plt
plt.plot(<X AXIS VALUES HERE>, <Y AXIS VALUES HERE>, 'line type', label='label here')
plt.plot(<X AXIS VALUES HERE>, <Y AXIS VALUES HERE>, 'line type', label='label here')
plt.legend(loc='best')
plt.show()