Matt, I am getting this error. I see that 'get_args' is defined in the ParticleIOHandlerRegion class, and a '_get_args' for ParticleIOHandlerSphere. I'm guessing that it should be '_get_args' under ParticleIOHandlerRegion. Thoughts? File "/home/sskory/yt/lib/python2.6/site-packages/yt-1.6dev-py2.6-linux-x86_64.egg/yt/lagos/HaloFinding.py", line 1114, in __init__ data = self._data_source.particles["particle_position_x"] File "/home/sskory/yt/lib/python2.6/site-packages/yt-1.6dev-py2.6-linux-x86_64.egg/yt/lagos/ParticleIO.py", line 47, in __getitem__ self.get_data(key) File "/home/sskory/yt/lib/python2.6/site-packages/yt-1.6dev-py2.6-linux-x86_64.egg/yt/lagos/ParticleIO.py", line 74, in get_data rtype, args = self._get_args() AttributeError: 'ParticleIOHandlerPeriodicRegionStrict' object has no attribute '_get_args' _______________________________________________________ sskory@physics.ucsd.edu o__ Stephen Skory http://physics.ucsd.edu/~sskory/ _.>/ _Graduate Student ________________________________(_)_\(_)_______________