How can I reassign or move vertexes of a vertex group How can I update/modify the xyz coordinates of a vertex group. 
I can get the vertex coordinates of the vertex group. BUT, what I want to do is reassign or move the vertex coordinates to a new list of coordinates.

I'm completely lost. It seems that I have the right context and data, but then I cannot figure out how to update/change the coords of the vertices. I've tried a number of things.

So here is the code raw. I first get the coords of the target vertices which are selected in the viewport (object), then I 'get' and print the vertices of the vertex group that I want to update coordinates to (see code).
BUT I can't figure out how to update the vertex coordinates. It's probably a noob easy-do but I can't figure it out!! Any help thanks!!! I'm going crazy here trying to figure this out.

import bpy
import bmesh

obj = bpy.context.active_object
objdata = bpy.context.active_object.data

vertices = obj.data.vertices
vertstarg = [obj.matrix_world * vert.co for vert in vertices] 

# coordinates as tuples if needed
vertstargtup = [vert.to_tuple() for vert in vertstarg]
#print(vertstarg)

#bpy.ops.object.select_all(action='DESELECT')
for obj in bpy.data.objects:
    obj.select = False

#holy cow. have to make the object active before selecting. makes sense now.
bpy.context.scene.objects.active = bpy.data.objects['crvface.001']  
bpy.data.objects['crvface.001'].select = True

obcage = bpy.context.object

bpy.ops.object.mode_set(mode='EDIT')
bpy.ops.mesh.select_all(action = 'DESELECT')
bpy.ops.object.vertex_group_set_active(group='cagefacepts')
bpy.ops.object.vertex_group_select()

vgVerts = [ v for v in obcage.data.vertices if v.select ]

print(vgVerts)

#Ok so clearly I can access the vertices of obcage.data vertex group, 
#but how to I update the coords from objcage.data.vertices to the list from
#vertstarg, which is a list of vector coords [or tuples if needed]???
tuples are read only you cant reasign its value. 
try to use to_list() instead... i think.
[list(vert) for vert in  vertstarg]
then seems like you are doing nothing to your verts but selecting 

grab the header bar down (the file menu) to see some info from operators. or go to de scripting window, there is on the top also.
almost every thing you do inside blender is shown on that "console"
see https://www.youtube.com/watch?v=2j75AM1Mttc