#!/usr/bin/env python
# coding: utf-8

# In[1]:


import sys
print(sys.version)


# In[2]:


from time import sleep
from abc import ABC, ABCMeta, abstractmethod

def compute(obj, s):
    print(f"Computing {s} of {obj} ...", end="")
    sleep(3)
    print("DONE!")
    return "Phew, that was a lot of work!"

class MyMetaClass(ABCMeta):
    @property
    def expensive_metaclass_property(cls):
        """This may take a while to compute!""" 
        return compute(cls, "metaclass property")
    
class MyBaseClass(ABC, metaclass=MyMetaClass):
    @classmethod
    @property
    def expensive_class_property(cls):
        """This may take a while to compute!"""
        return compute(cls, "class property")
    
    @property
    def expensive_instance_property(self):
        """This may take a while to compute!"""   
        return compute(self, "instance property")

class MyClass(MyBaseClass):
    """Some subclass of MyBaseClass"""
    
help(MyClass)