How to change a *VectorProperty size?

Question

Let's say I've created a scene property named a:

bpy.types.Scene.a = bpy.props.IntVectorProperty(
    name='a',
    description="Frequencies",
    size=2,
    default=[1, 2]
)

And now I would like to update it's size to something else.

• How can I do that?
• Do I have to override the property? What if instead of a single property I have a PropertyGroup and I want to update an IntVectorProperty that belongs to the group?

Answer 1

Have you seen Property Definitions? IntVectorProperty have other parameters to define, among which no "size"!

You can create a Custom property from PropertyGroup:

class CustomProperty(bpy.types.PropertyGroup):
    name: bpy.props.StringProperty(name="Name", default="Some name")
    description: bpy.props.StringProperty(name="Description", default="Frequencies")
    size: bpy.props.IntProperty(name="Size", default=2)

To update any property just assign some value:

bpy.types.Scene.a = 3

Answer 2

from bpy.props import CollectionProperty, IntVectorProperty, StringProperty
from bpy.types import AddonPreferences

classes = []

def CreatVectorProp(size, name, vectortyp):
    exec("bpy.types.Scene.%sproperty_%s = %sProperty(size= size)" % (vectortyp.lower(), name, vectortyp)) 
    return "bpy.context.scene.%sproperty_%s" %(vectortyp.lower(), name)

def AddNewElementToCollection():
    new = bpy.context.scene.MyCollection.add()
    new.address = CreatVectorProp(10, "MyIntVector", "IntVector")
    new.otherprops = "other stuff"

def RemoveElementfromCollection(index):
    exec("del bpy.types.Scene.%s" % bpy.context.scene.MyCollection[index].address.split(".")[-1])
    bpy.context.scene.MyCollection.remove(index)

def UpdateVector(index, newsize):
    exec("del bpy.types.Scene.%s" % bpy.context.scene.MyCollection[index].address.split(".")[-1])
    bpy.context.scene.MyCollection[index].address = CreatVectorProp(newsize, "MyNewVector", "IntVector")

def AssignValues(index, values):
    exec("%s = values" % bpy.context.scene.MyCollection[index].address)

def GetValues(index):
    return eval(bpy.context.scene.MyCollection[index].address)

class MyProperty(bpy.types.PropertyGroup):
    address : StringProperty()
    otherprops : StringProperty()
classes.append(MyProperty)

def register():
    for cls in classes:
        bpy.utils.register_class(cls)
    bpy.types.Scene.MyCollection = CollectionProperty(type= MyProperty)

def unregister():
    for ele in bpy.context.scene.MyCollection:
        exec("del bpy.types.Scene.%s" % ele.address.split(".")[-1])
    del bpy.types.Scene.MyCollection
    for cls in classes:
        bpy.utils.unregister_class(cls)

Something like this should do the trick. (Tested on version 2.83.3)