Hi, 1) I need to get residue.areaSES for two separate selections (all polar amino acids and all nonpolar amino acids). I have successfully generated a list of residue.areaSES using the GUI simply by selecting the residues of interest and then using the attribute calculator typing "residue.areaSES" in the formula box of the Attribute Calculator, which outputs the list to the Reply Log. This is the data that I need, but I need to get it for >2000 PDB structures and would like to automate this analysis through a Python script. I am somewhat new to Python and Chimera and don't yet know all the ins and outs yet. I dug through the code and found a method "getResidueAttr" in the "ResidueDataWrapper" class from "CalcAttr". This seems to be what I need, but I don't know the proper syntax to call it from my Python script. Could someone please provide an example? 2) I would like to sum the residue.areaSES values once I have them. I tried "sum(residue.areaSES)" in the formula box of the Attribute Calculator in the GUI, but this returns the error "Formula evaluation error: expecting vector argument in function". I'm not sure again on the proper syntax to use "sum()" in the Attribute Calculator. If I knew how to generate/save the residue.areaSES data from the command line, I could just parse the saved file and sum the values in Python. How can Attribute Calculator formulas be used from the command line, and if they can't, how can I save the residue.areaSES data to file from a Python script? Thanks in advance, Roger -- Roger L. Chang Graduate Student Bioinformatics and Systems Biology Graduate Program University of California, San Diego