PyPlot move alternative y axis to background

Question

In pyplot, you can change the order of different graphs using the zorder option or by changing the order of the plot() commands. However, when you add an alternative axis via ax2 = twinx(), the new axis will always overlay the old axis (as described in the documentation).

Is it possible to change the order of the axis to move the alternative (twinned) y-axis to background?

In the example below, I would like to display the blue line on top of the histogram:

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

# Data
x = np.arange(-3.0, 3.01, 0.1)
y = np.power(x,2)

y2 = 1/np.sqrt(2*np.pi) * np.exp(-y/2)
data = [random.gauss(0.0, 1.0) for i in range(1000)]

# Plot figure
fig = plt.figure()
ax1 = fig.add_subplot(111)
ax2 = ax1.twinx()

ax2.hist(data, bins=40, normed=True, color='g',zorder=0)
ax2.plot(x, y2, color='r', linewidth=2, zorder=2)
ax1.plot(x, y, color='b', linewidth=2, zorder=5)

ax1.set_ylabel("Parabola")
ax2.set_ylabel("Normal distribution")

ax1.yaxis.label.set_color('b')
ax2.yaxis.label.set_color('r')

plt.show()

Edit: For some reason, I am unable to upload the image generated by this code. I will try again later.

Answer 1

You can set the zorder of an axes, ax.set_zorder(). One would then need to remove the background of that axes, such that the axes below is still visible.

ax2 = ax1.twinx()
ax1.set_zorder(10)
ax1.patch.set_visible(False)