Hello @i_mazlov!

Thank you so much for your fast and thoughtful answer, I'm sorry if I didn't post to the right place or in the right form. I'm going to read the rules of the forum more.
I'm more a designer than a developer but I understand the solution path you provided to me and I truly appreciate it! Do you know anything about the CV-parametric selection tag from Cineversity?

I actually found something that would help me A LOT but I can't find it anywhere online! what I described is what is possible with this python script:
CV-Parametric Selection Tag for Cinema 4D from Cineversity! I tried to find it but it's impossible to get my hand on it! can someone help please!

So... I have a little problem, I have made a grid of objects made with Voronoi Fracture, and I'm trying to assign a material to each individual polygon from the fracture object. I can't see a way to assign a material based on the number index of a cloner/fracture object/voronoi object or create a list of selection tag on the voronoi fracture...
I wish that the index number could be a variable that we could use as a selection or tag! If anyone has an idea of how to tackle this issue, I would love to hear you out, this is what I have so far:

import c4d
def main():
    # Get the active object, which should be a Voronoi Fracture object
    fracture_obj = doc.GetActiveObject()
    # Check if the object is a Voronoi Fracture object
    if fracture_obj is None or not fracture_obj.CheckType(c4d.Ofracture):
        raise RuntimeError("Please select a Voronoi Fracture object.")
    # Access the children of the Voronoi Fracture object (these are the fractured pieces)
    fracture_pieces = fracture_obj.GetChildren()
    # Ensure there are fracture pieces
    if not fracture_pieces:
        raise RuntimeError("No fracture pieces found. Please ensure the Voronoi Fracture is applied to an object.")
    # Loop through each fracture piece
    for i, piece in enumerate(fracture_pieces):
        # Create a unique polygon selection tag for each piece
        selection_tag = piece.MakeTag(c4d.Tpolygonselection)
        selection_tag.SetName(f"Piece_{i}_Selection")
        # Select all polygons of this fracture piece
        poly_selection = c4d.BaseSelect()
        poly_count = piece.GetPolygonCount()
        for poly_index in range(poly_count):
            poly_selection.Select(poly_index)
        # Assign the selection to the tag
        selection_tag.SetBaseSelect(poly_selection)
    # Refresh the scene to apply the changes
    c4d.EventAdd()
# Execute the script
if __name__ == '__main__':```