O, I have this Collection Property:

class particle_instancer(bpy.types.PropertyGroup):
    particle_object = StringProperty (name = "Object", description = "")
    particle_material = StringProperty (name = "Material", description = "")

bpy.types.Scene.particle_instancer = CollectionProperty(type = particle_instancer)  

And then I have an operator that is supposed to add a StringProperty() to its first item.

If Instead of a CollectionProperty I used the scene as the "Container" for the properties, I could simply do:

bpy.types.Scene.my_prop = StringProperty()

I thought I could do:

bpy.types.particle_instancer.my_prop = StringProperty()

But this leads to nothing as the property doesn't get register and it doesn't give me any error StackTrace neither. So is it possible to do? If yes how could I do?


2 Answers 2


You can add properties to the PropertyGroup as follows:

bpy.types.Scene.particle_instancer[1]['type'].my_prop = bpy.props.StringProperty()

Internally, your bpy.types.Scene.particle_instancer is a tuple that will look like this:

(<built-in function CollectionProperty>, {'type': <class '__main__.particle_instancer'>, 'attr': 'particle_instancer'})

So, you can index the dict giving you access to the particle_instancer class, where you can add properties.

I got the idea to access the 'type' from this answer: https://blender.stackexchange.com/a/28091/20051


You can only assign values or add new class attributes per item.

import bpy

class CustomGroup(bpy.types.PropertyGroup):
    id = bpy.props.IntProperty()
    foo = bpy.props.StringProperty()

bpy.types.Scene.custom_group = bpy.props.CollectionProperty(type=CustomGroup)

>>> item = bpy.context.scene.custom_group.add()
>>> item.id = 0
>>> item.name = "Cube"
>>> item.foo = "Sphere"
>>> item.foo
>>> 'Sphere'
  • 2
    $\begingroup$ I was able to add new class attributes with bpy.types.Scene.custom_group[1]['type'].my_new_prop = ... $\endgroup$ Dec 7, 2018 at 6:07

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