I have a list of positions that I call xwclump, ywclump, and zwclump.  I have been selecting regions in a loop using ds.sphere and the center: data_source = ds.sphere([xwclump[j]/(300.*3.086e21),ywclump[j]/(300.*3.086e21),zwclump[j]/(300.*3.086e21)],(1000,'pc'))  (the divisor is to put the center into code units).  This works fine.

But, when I try to use cut_region: data_source = ad.cut_region(["(obj['temperature'] > 1.0e6) & (obj['z'] < (zwclump[j]/(300.*3.086e21)))"]) I get an error: 

NameError: name 'zwclump' is not defined

Is this something anyone else has dealt with?  If it doesn't ring any bells I will try and break IsolatedGalaxy and send the code snippet...