I am experimenting with my idea for utilizing a _draworder attribute in Collection objects. Since not everything in a collection is guaranteed to be the same length or even be numpy arrays, I have to add some logic to coerce everything to numpy arrays and tile their data so that the length of their first axis match up. I also have logic to convert all objects back to their original types prior to continuing, just in case that makes any difference. However, using AGG seems to fail here: Traceback (most recent call last): File "/home/ben/miniconda/lib/python2.7/site-packages/nose/case.py", line 197, in runTest self.test(*self.arg) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/testing/decorators.py", line 51, in failer result = f(*args, **kwargs) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/testing/decorators.py", line 183, in do_test figure.savefig(actual_fname, **self._savefig_kwarg) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/figure.py", line 1490, in savefig self.canvas.print_figure(*args, **kwargs) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backend_bases.py", line 2211, in print_figure **kwargs) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_agg.py", line 525, in print_png FigureCanvasAgg.draw(self) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_agg.py", line 472, in draw self.figure.draw(self.renderer) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/artist.py", line 60, in draw_wrapper draw(artist, renderer, *args, **kwargs) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/figure.py", line 1094, in draw func(*args) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/mpl_toolkits/mplot3d/axes3d.py", line 273, in draw ax.draw(renderer) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/mpl_toolkits/mplot3d/axis3d.py", line 370, in draw self.gridlines.draw(renderer, project=True) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/mpl_toolkits/mplot3d/art3d.py", line 203, in draw LineCollection.draw(self, renderer) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/artist.py", line 60, in draw_wrapper draw(artist, renderer, *args, **kwargs) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/collections.py", line 345, in draw self._offset_position) File "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_agg.py", line 127, in draw_path_collection return self._renderer.draw_path_collection(*kl, **kw) SystemError: new style getargs format but argument is not a tuple The PDF and SVG backends aren't experiencing this problem. I have taken out the parts of my code that "broadcasted" the arrays, and the error still happens. I then took out the code that coerced everything to numpy arrays in the first place, and the error disappeared (taking that out effectively let everything pass through unaffected). Keep in mind that my code coerced everything back to their original types prior to calling the renderer, so it was merely the action of converting stuff into an array that did this. The best I can figure is that there is something wrong with the C++ code for our agg wrapper? Googling the exception message brings up various discussions of mistakes in the argument handling of C/C++ code. I haven't a clue, though, why this would be an issue. Thoughts? Ben Root