Regions

Regions are structural subsets (selections) you can represent, hide/show, and delete independently.

Use regions when you need multiple representations at once (for example, protein as cartoon and ligand as ball-and-stick). Use presets from Representations to stay consistent across regions.

Create a region from a selection

import molsysviewer as viewer

view = viewer.MolSysView()
view.load("1CRN")
view.show()

protein = view.new_region("protein", tag="protein", representation="cartoon")
ligand = view.new_region("hetero", tag="ligand", representation="ball-and-stick")

Update a region representation

ligand.set_representation("spacefill", alpha=0.5)

You can also apply a Mol* preset (or a user preset if configured):

protein.set_representation(preset="polymer-cartoon")

Hide/show and delete

ligand.hide()
ligand.show()
ligand.delete()

Complementary regions

If you want “everything except X”, create a new region from the complement:

binding_site = view.new_region("resid 10:20", tag="site", representation="ball-and-stick")
rest = binding_site.new_complementary_region(tag="not-site", representation="cartoon")