'Selected' polygons are not selected?

Question

I am struggling to learn Blender, so bear with me...

Simple idea: select one (or more) vertices. Run the code, and all polygons connected to the vertex/vertices should be selected.

The code appears to work, in the sense that all effected polygons/faces get 'colored', therefore - in my mind - are 'selected'.

However, the very last line shows only False's for all polygons. I must be missing something here...

import bpy
import bmesh

#----------        
def get_sel_vertices(me):
    sel_verts = [v for v in me.vertices if v.select]
    return sel_verts
#----------
# From selected vertices, select all polygons linked to those vertices (edit mode)
def vtx_get_sel_polygons(od):
    bm = bmesh.from_edit_mesh(od)
    poly = []
    for f in bm.faces:
        for v in f.verts:
            lf = v.link_faces
            if v.select:
                poly.append(f)        
    
    for p in poly:
        p.select = True
    
    bmesh.update_edit_mesh(ob.data)
    return len(poly) # Number of polys
#----------

ob = bpy.context.object
print("")

if ob.type != 'MESH':
    raise TypeError("Active object is not a Mesh")

# Get editmode changes
ob.update_from_editmode()

me = ob.data

vsel = get_sel_vertices(me)
        
if len(vsel):
    print('Selected v: ', len(vsel))
    
    polys = vtx_get_sel_polygons(me) # Select all connected polygons
    print('Selected p: ', polys)
    
    print([x.select for x in me.polygons]) # Every select shows up as False???

Answer 1

The reason why it's happening is because you are tying to get the vertices/polygons data from edit mode, which is not possible by directly accessing mesh components. There are several ways to fix it:

Change interpolation mode to OBJECT and back to EDIT(brute force)

import bpy
import bmesh
     
def get_sel_vertices(me):
    bpy.ops.object.mode_set(mode='OBJECT') # Go to OBJECT
    sel_verts = [v for v in me.vertices if v.select]
    bpy.ops.object.mode_set(mode='EDIT') # Go back
    return sel_verts

...
        
if len(vsel):
    print('Selected v: ', len(vsel))
    
    polys = vtx_get_sel_polygons(me)
    print('Selected p: ', polys)
    
    bpy.ops.object.mode_set(mode='OBJECT') # Go to OBJECT
    print([x.select for x in me.polygons])
    bpy.ops.object.mode_set(mode='EDIT') # Go back

Using BMesh(cleaner)

import bpy
import bmesh

bm = bmesh.from_edit_mesh(bpy.context.active_object.data)

sel_faces = [f for f in bm.faces if f.select]
sel_verts = [v for v in bm.verts if v.select]

Using BMesh method I assume that the object will be in Edit Mode. Hope it helps!