On Sun, Mar 27, 2011 at 8:25 PM, Angus McMorland <amcmorl@gmail.com> wrote:
On 27 March 2011 20:47, Warren Weckesser <warren.weckesser@enthought.com> wrote:
> I'm using matplotlib 1.0.1.  I have the following simple script to plot a
> surface:
>
> -----
> from numpy import linspace, sin, cos, meshgrid
>
> from matplotlib.pyplot import figure, show, xlabel, ylabel
> from matplotlib import cm
> from mpl_toolkits.mplot3d import Axes3D
>
> n = 35
> x = linspace(-5, 5, n)
> y = linspace(0, 10, n)
> X, Y = meshgrid(x, y)
> Z = X*sin(X)*cos(0.25*Y)
>
> fig = figure()
> ax = fig.gca(projection='3d')
> ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap=cm.copper)
> xlabel('x')
> ylabel('y')
> show()
> -----
>
> It works fine--many thanks to all the folks working on the 3D plots!
>
> But notice that Axes3D is imported from matplotlib.mplot3d, but never
> explicitly used.  If I comment out that import, however, I get the following
> traceback:
> -----
> Traceback (most recent call last):
>   File "surf_demo.py", line 15, in <module>
>     ax = fig.gca(projection='3d')
>   File
> "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib/figure.py",
> line 965, in gca
>     return self.add_subplot(111, **kwargs)
>   File
> "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib/figure.py",
> line 675, in add_subplot
>     projection_class = get_projection_class(projection)
>   File
> "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/matplotlib/projections/__init__.py",
> line 61, in get_projection_class
>     raise ValueError("Unknown projection '%s'" % projection)
> ValueError: Unknown projection '3d'
> -----
>
> Is this expected?

Yes, the last lines of axes3d.py, which get called when Axes3D is imported, are:

import matplotlib.projections as proj
proj.projection_registry.register(Axes3D)

which is what lets matplotlib know about the '3d' projection. Just
importing the Axes3D module therefore performs the necessary
registration of the projection to be able to use it in subsequent
code. Code analysis tools like rope don't know about this behind the
scenes stuff though, so it looks like a redundant import to them.


OK, thanks.

Warren
 

Angus.
--
AJC McMorland
Post-doctoral research fellow
Neurobiology, University of Pittsburgh