Blender - Replace materials with _ to . (For Alembic workflow)

import bpy
import re

# Pattern: match names ending with _### (like _001, _002, etc.)
pattern = re.compile(r"(.*)_(\d{3})$")

for obj in bpy.data.objects:
    if not obj.data or not hasattr(obj.data, "materials"):
        continue

    for i, mat in enumerate(obj.data.materials):
        if mat is None:
            continue

        match = pattern.match(mat.name)
        if match:
            base, num = match.groups()
            new_name = f"{base}.{num}"

            # Check if target material exists
            new_mat = bpy.data.materials.get(new_name)
            if new_mat:
                print(f"Replacing {mat.name} → {new_name} on {obj.name}")
                obj.data.materials[i] = new_mat
            else:
                print(f"Target material not found: {new_name}")