Scaling/Rezise in Blender 2.8 Python/Script not working on mesh

Question

I am working on a scrip that makes tiles (like for a kitchen floor). I have a script that works perfect on planes for 4 sided tiles. However, I am running into an issues on non-4 sided tiles.

I chose to use cylinders which almost exactly works as needed. But I am hitting an issue on "beveling" (which is just scaling 1 of the faces) the top face of the cylinder.

My code looks at all the faces on the mesh, and

-if it does equal 4 sides, then the script deselects them.

-If it does not equal 4 sides, then runs another check

-If we haven't deleted any faces yet, then it deletes 1 face

-If we have deleted 1 face, then we are on the top face Up to this point works perfectly together

-Then the script scales in the selected face This is where it causes issues

The scaling code works fine on its own if I manually select a face first, and also works fine by hand. I'm not sure if it's a bug or something I'm missing but I could use any help my fellow blender scripters can offer.

I'm including just the face adjusting part of the script, so to test my code you'll have to Add > Mesh > Cylinder to test it out.

Thank you! (see code and images below)

#Import Python
import bpy
#Import mesh handling
import bmesh
#Import vector
from mathutils import Vector


tileBevelZ = 0.85

#_________________________________________Delete the bottom face

#edit mode
bpy.ops.object.mode_set( mode   = 'EDIT'   )

#number of faces we've deleted
facesDeleted = 0
#our current object
obj = bpy.context.object
#ref to mesh
bm = bmesh.from_edit_mesh(obj.data)


#for each face in mesh
for f in bm.faces:
    #if it's selected
    if f.select == True:
        #if it does not have the number of sides we want
        if len(f.verts) == 4:
            #we dont want to select it
            f.select = False
        # else if it does have the same number of sides    
        else:
            #if we have not deleted a side yet
            if facesDeleted == 0:
                #deslect 1 of the faces
                f.select = False
                #increase faces deleted
                facesDeleted += 1
            #else if we increased our counter    
            else:
                #make sure it's selected
                f.select = True
                #Delete the face
                bpy.ops.mesh.delete(type='FACE')

#set mode to faces
bpy.ops.mesh.select_mode( type  = 'FACE'   )
#select all                
bpy.ops.mesh.select_all(action='SELECT')

#_________________________________________Adjust scale of top face for bevel            
#for each face in mesh
for f in bm.faces:
    #if it's selected
    if f.select == True:
        #if it does not have the number of sides we want
        if len(f.verts) == 4:
            #we dont want to select it
            f.select = False
        # else if it does have the same number of sides    
        else:
            #make sure it's selected
            f.select = True
            #set mode to vertices
            bpy.ops.mesh.select_mode( type  = 'FACE'   )
            #Scale the face in
            bpy.ops.transform.resize(value=(tileBevelZ , tileBevelZ , tileBevelZ), orient_type='GLOBAL', orient_matrix=((1, 0, 0), (0, 1, 0), (0, 0, 1)), orient_matrix_type='GLOBAL', mirror=True, use_proportional_edit=False, proportional_edit_falloff='SMOOTH', proportional_size=1, use_proportional_connected=False, use_proportional_projected=False)

Answer 1

Another take on getting the result.

Rather than trying to debug what is happening with your question script here is another take to achieve what I believe is the desired result.

Test script, object mode, adds a cylinder, removes bottom face, scales top face.

Bottom and top faces have z component to their normals. This is how they are selected below.

Once selected, the bottom face is removed from the faces collection.

Scaling top face similar to related question Using python and bmesh to scale/resize a face in place , in this case, using bmesh.ops.scale

Notice apart from adding the cylinder to test, there is no bpy.ops used.

import bpy
import bmesh
from mathutils import Matrix

scale_factor = 0.85

# add a cylinder to test

bpy.ops.mesh.primitive_cylinder_add()
ob = bpy.context.object
me = ob.data
bm = bmesh.new()
bm.from_mesh(me)

top_face = [f for f in bm.faces if f.normal.z > 0.5].pop()

bottom_face = [f for f in bm.faces if f.normal.z < 0.5].pop()

# remove bottom face

bm.faces.remove(bottom_face)

# scale top face 

bmesh.ops.scale(bm,
        vec = (scale_factor,) * 3,
        space = Matrix.Translation(-top_face.calc_center_median()),
        verts = top_face.verts)

bm.to_mesh(me)
me.update()

Note bmesh.ops.create_cone(diameter1=1, diameter2=0.85) could be used to create the shape, removing the need to scale.

Suggestion, don't over comment code, and consider using if f.select: instead of if f.select == True: