“cmd.distance” creates a new distance object between two selections.

cmd.distance(string name, string selection1, string selection2,
             string cutoff, string mode )

def distance(name=None, selection1="(pk1)", selection2="(pk2)", 
		 cutoff=None, mode=None, zoom=0, width=None, length=None,
             gap=None, label=1, quiet=1, reset=0, state=0):

distance | api