Un moyen simple de mettre en cache la valeur dans le décorateur de propriété. En lecture seule. Notez qu'il conserve la mise en cache jusqu'à ce que l'objet soit supprimé.

def cached_ro_property(f):
    cache = [None]
    def _cached_ro_property(*args, **kargs):
        if cache[0]:
            return cache[0]
        cache[0] = f(*args, **kargs)
        return cache[0]
    return property(_cached_ro_property)


from django.test import TestCase
import mox


class TestCachedRoProperty(TestCase):
    """Test for cached_ro_property decorator."""
    
    def setUp(self):
        self.m = mox.Mox()

    def tearDown(self):
        self.m.UnsetStubs()
        self.m = None

    def test_call_1(self):
        """Simple call."""

        from decorators import cached_ro_property

        # Procuder function that should be called once.
        producer = self.m.CreateMockAnything()
        producer().AndReturn(30)

        class C(object):
            @cached_ro_property
            def f(self):
                return producer()

        self.m.ReplayAll()
        c = C()

        self.assertEqual(c.f, 30)
        self.assertEqual(c.f, 30)
        self.m.VerifyAll()

    def test_call_2(self):
        """Check that property function reference self."""

        from decorators import cached_ro_property

        # Procuder function that should be called once.
        producer = self.m.CreateMockAnything()
        producer().AndReturn(30)

        class C(object):
            @cached_ro_property
            def f(self):
                return self.g()
            def g(self):
                return producer()

        self.m.ReplayAll()
        c = C()

        self.assertEqual(c.f, 30)
        self.assertEqual(c.f, 30)
        self.m.VerifyAll()