Layers.md

Layers - how to set

instead of writing

.....,layers=[True, False, False ..........False]

You can write it more Pythonic

# if you want the object on 1 layer
.....,layers=[i in {0} for i in range(20)]

# if you want the object on multiple layers
.....,layers=[i in {0,1,4,12} for i in range(20)]
>>> [True, True, False, False, True, False, False, ...., True, ....False, False]

Moving objects from one layer to another

Moving objects that appear in one range of layers, to another range.

import bpy

for obj in bpy.data.objects:
    
    # let's deal with a simple case: is it only on one layer?
    if obj.layers[:].count(True) == 1:
        found_index = obj.layers[:].index(True)
        if (5 <= found_index <= 10):
            new_index = found_index + 5
            obj.layers[:] = [i==new_index for i in range(20)]

Here restated with a new function called set_layer, to encapsulate the behavior. It's less efficient, but arguably easier to read.

import bpy

def set_layer(obj, idx):
    obj.layers[:] = [i==idx for i in range(20)]

for obj in bpy.data.objects:
    if obj.layers[:].count(True) == 1:
        found_index = obj.layers[:].index(True)
        if found_index in {5,6,7,8,9}:
            set_layer(obj, found_index + 5)

Here's an alternative, which might be interesting if you're new to python

import bpy

only_on_one_layer = lambda o: o.layers[:].count(True) == 1

for o in filter(only_on_one_layer, bpy.data.objects):
    layer_id = o.layers[:].index(True)
    if layer_id in {5,6,7,8,9}:
        o.layers[:] = [i == (layer_id + 5) for i in range(20)]