Example of using class and instance attribute, showing the implications in the context of operator lifetime

class_vs_instance_attribute.py

bl_info = {
    "name": "Class vs Instance Attribute",
    "author": "Robert Guetzkow",
    "version": (1, 0),
    "blender": (2, 80, 0),
    "location": "",
    "description": "Demonstrates the lifetime of the operator.",
    "warning": "",
    "wiki_url": "",
    "category": "3D View"}

import bpy


class EXAMPLE_OT_class_attribute(bpy.types.Operator):
    bl_idname = "example.class_attribute"
    bl_label = "Increment and print class attribute"
    bl_description = "Increment and print instance attribute"

    x = 0

    def execute(self, context):
        EXAMPLE_OT_class_attribute.x += 1
        print(f"EXAMPLE_OT_class_attribute: {EXAMPLE_OT_class_attribute.x}")
        return {"FINISHED"}
    
class EXAMPLE_OT_instance_attribute(bpy.types.Operator):
    bl_idname = "example.instance_attribute"
    bl_label = "Increment and print instance attribute"
    bl_description = "Increment and print instance attribute"
    
    def __init__(self):
        self.x = 0

    def execute(self, context):
        self.x += 1
        print(f"self.x: {self.x}")
        return {"FINISHED"}

classes = (EXAMPLE_OT_class_attribute, EXAMPLE_OT_instance_attribute)


def register():
    for cls in classes:
        bpy.utils.register_class(cls)


def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)


if __name__ == "__main__":
    register()
    
    for i in range(5):
        bpy.ops.example.class_attribute()
        
    for i in range(5):
        bpy.ops.example.instance_attribute()