This command will return a python list of chains for the given selection.
Proteins structures often have more than one chain of residues present in a structure file. This command will fetch the names of each chain present. Because of the lack of standards, sometimes chain A will also be blank "". This isn't a problem for PyMOL, but be warned sometimes you may get back, [""].
# using get_chains for the object or selection called objSel get_chains objSel
# examples fetch 1cll print "1CLL has the following chains:", cmd.get_chains("1cll") # list all chains in all proteins loaded in PyMOL: for x in cmd.get_names(): for ch in cmd.get_chains(x): print x, " has chain ", ch