Hi Diana, If m is your model, then the list of polymeric chain IDs is m.chains.chain_ids. If you want all chain IDs including those containing only ligands/water, try m.residues.unique_chain_ids. Best regards, Tristan ________________________________ From: ChimeraX-users <chimerax-users-bounces@cgl.ucsf.edu> on behalf of Diana Lee via ChimeraX-users <chimerax-users@cgl.ucsf.edu> Sent: 29 June 2021 19:44 To: chimerax-users@cgl.ucsf.edu <chimerax-users@cgl.ucsf.edu> Subject: [chimerax-users] Accessing Chain IDs Hi team! I have what I hope is an easy question. I'm accessing ChimeraX commands via python script, and I need a list of the Chain IDs. I'm currently getting the number of chains using the num_chains property. I've done quite a bit of digging through documentation and can only find ways to rename, or view interfaces, but I can't seem to find any specific command to list them. I feel as though it must be so basic, no one has needed to ask. :) Thanks for your help, Diana Lee Graduate Student Luque Lab, SDSU VII