Vertex coordinate after pose change I am working with a makehuman model in blender. To change the pose of the model I modify the scale and rotation parameters of the bones. The code looks similar to 

bpy.context.object.pose.bones['hand.fk.R'].rotation_euler[0] = 0


My goal is now to get the location of a specific vertex after some pose changes. I already tried to transform the vertex location with the object world matrix

bpy.data.objects['makehuman'].matrix_world * v.co


but since the world matrix is an identity matrix the result is the same independent from the current pose.

How can I derive the vertex location after a pose change, or is it even possible?
You can use Object.to_mesh() to create a mesh datablock, which has deformations and modifiers applied. Mesh.transform() that with .matrix_world for world space:

import bpy

C = bpy.context
ob = C.object

print(ob.data.vertices[0].co, "- Vert 0 (original)")

me = ob.to_mesh(scene=C.scene, apply_modifiers=True, settings='PREVIEW')
print(me.vertices[0].co, " - Vert 0 (deformed/modified)")

me.transform(ob.matrix_world)
print(me.vertices[0].co, " - Vert 0 (deformed/modified, world space)")

bpy.data.meshes.remove(me)


Note that vertex indices may differ after modifiers are applied (e.g. Array, Bevel, ...).

Alternatively, the bmesh module can be used to achieve the same as the above script.