Select Source of Constrained Object

select_constraint_source.py

# Select source of selected constrained object
from maya import cmds

selection = cmds.ls(sl=1)
new_selection = []
for item in selection:
   constraint = cmds.listConnections( item + '.parentInverseMatrix[0]', destination=1, source=0, type='constraint')
   if constraint:
      src = cmds.listConnections(constraint[0] + '.target[0].targetParentMatrix', destination=0, source=1)
      if src:
         new_selection.extend(src)
if new_selection:
    cmds.select(new_selection)