python - How to create a legend for 3D bar in matplotlib? -

given ax = plt.subplot():

ax.bar()[0] can passed plt.legend().

however, ax.bar3d() returns none. how create legend displayed bars?

update:

passing legend="stuff" ax.bar3d() , calling ax.legend() raises

/usr/lib/python2.6/site-packages/matplotlib/axes.py:4368: userwarning: no labeled objects found. use label='...' kwarg on individual plots. warnings.warn("no labeled objects found. " 

you need use proxy artist legends not supported.

this code:

from mpl_toolkits.mplot3d import axes3d import matplotlib.pyplot plt import numpy np  fig = plt.figure() ax = fig.add_subplot(111, projection='3d') x, y = np.random.rand(2, 100) * 4 hist, xedges, yedges = np.histogram2d(x, y, bins=4)  elements = (len(xedges) - 1) * (len(yedges) - 1) xpos, ypos = np.meshgrid(xedges[:-1]+0.25, yedges[:-1]+0.25)  xpos = xpos.flatten() ypos = ypos.flatten() zpos = np.zeros(elements) dx = 0.5 * np.ones_like(zpos) dy = dx.copy() dz = hist.flatten()  ax.bar3d(xpos[:8], ypos[:8], zpos[:8], dx, dy, dz, color='b', zsort='average') blue_proxy = plt.rectangle((0, 0), 1, 1, fc="b") ax.bar3d(xpos[8:], ypos[8:], zpos[8:], dx, dy, dz, color='r', zsort='average') red_proxy = plt.rectangle((0, 0), 1, 1, fc="r") ax.legend([blue_proxy,red_proxy],['cars','bikes'])  plt.show() 

produces this: