How to determine the projection (2D or 3D) of a matplotlib axes object?

Question

In Python's matplotlib library it is easy to specify the projection of an axes object on creation:

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
ax = plt.axes(projection='3d')

But how do I determine the projection of an existing axes object? There's no ax.get_projection, ax.properties contains no "projection" key, and a quick google search hasn't turned up anything useful.

Answer 1

I don't think there is an automated way, but there are obviously some properties that only the 3D projection has (e.g. zlim).

So you could write a little helper function to test if its 3D or not:

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt

def axesDimensions(ax):
    if hasattr(ax, 'get_zlim'): 
        return 3
    else:
        return 2


fig = plt.figure()

ax1 = fig.add_subplot(211)
ax2 = fig.add_subplot(212, projection='3d')

print "ax1: ", axesDimensions(ax1)
print "ax2: ", axesDimensions(ax2)

Which prints:

ax1:  2
ax2:  3