Import normals doesn't work Trying to import model to Blender 2.67 using guide:

http://wiki.xentax.com/index.php/Blender_Import_Guide#Vertex_normals

But importing normals doesn't work. 

Code sample:

...
mesh = bpy.data.meshes.new(obname)
mesh.from_pydata(vlist, edges, faces)

from bpy_extras import object_utils
object_utils.object_data_add(context, mesh, operator=None)
...
vindex = 0
for vertex in mesh.vertices:
    vertex.normal = (0, 0, 1)
    vindex += 1


All normals must be oriented along z, but they seems to be random.
It seems like importing normals is impossible with 2.67 version of Blender. Blender recalculates them manually.

But for version 2.74 you can import custom normals using code sample:

normals2 = []
for l in mesh.loops:
    normals2.append(nlist[l.vertex_index])
mesh.normals_split_custom_set(normals2)
mesh.use_auto_smooth = True