memoize.py

from uuid import uuid4

_cache = {}

def cache_set(key, value):
    print 'Setting ', key, ' with value ', value
    _cache[key] = value

def cache_get(key):
    print 'Returning ', key, ' from cache'

    if key in _cache:
        print 'Cache hit!'
        return _cache[key]
    else:
        print 'Cache miss!'


def cache_property(instance_key):
    def decorated(method):
        def wrapped(instance):
            instance_cache_key = '{instance_prefix}:{instance_key}'.format(
                instance_prefix=instance._instance_cache_prefix(),
                instance_key=instance_key,
            )

            cached_value = cache_get(instance_cache_key)

            if cached_value is not None:
                return cached_value
            else:
                value = method(instance)
                cache_set(instance_cache_key, value)
                return value

        return property(wrapped)
    return decorated


class Book(object):

    def __init__(self, author, title):
        self.uid = uuid4().hex
        self.author = author
        self.title = title

    def _instance_cache_prefix(self):
        return self.uid

    @cache_property('title')
    def full_title(self):
        print 'Computing full title'
        return '{author} - {title}'.format(
            author=self.author,
            title=self.title,
        )

book1 = Book('JK Rowling', 'The Nerds Stone')

print book1.full_title
print book1.full_title

book2 = Book('Tolkien', 'The Nerds Tower')

print book2.full_title
print book2.full_title



output:
  
Returning  fd24815d90cf4c2692694e3a1bb91c93:title  from cache
Cache miss!
Computing full title
Setting  fd24815d90cf4c2692694e3a1bb91c93:title  with value  JK Rowling - The Nerds Stone
JK Rowling - The Nerds Stone
Returning  fd24815d90cf4c2692694e3a1bb91c93:title  from cache
Cache hit!
JK Rowling - The Nerds Stone
Returning  fd319e3f1f0c4c4e9882bbb497e19876:title  from cache
Cache miss!
Computing full title
Setting  fd319e3f1f0c4c4e9882bbb497e19876:title  with value  Tolkien - The Nerds Tower
Tolkien - The Nerds Tower
Returning  fd319e3f1f0c4c4e9882bbb497e19876:title  from cache
Cache hit!
Tolkien - The Nerds Tower