Merge branch 'ticket19872' of https://github.com/oinopion/django

    def __init__(self, func):

        self.func = func

    def __get__(self, instance, type):

    def __get__(self, instance, type=None):

        if instance is None:

            return self

        res = instance.__dict__[self.func.__name__] = self.func(instance)

        return res

from django.utils import unittest

from django.utils.functional import lazy, lazy_property

from django.utils.functional import lazy, lazy_property, cached_property

class FunctionalTestCase(unittest.TestCase):

        self.assertRaises(NotImplementedError, lambda: A().do)

        self.assertEqual(B().do, 'DO IT')

    def test_cached_property(self):

        """

        Test that cached_property caches its value,

        and that it behaves like a property

        """

        class A(object):

            @cached_property

            def value(self):

                return 1, object()

        a = A()

        # check that it is cached

        self.assertEqual(a.value, a.value)

        # check that it returns the right thing

        self.assertEqual(a.value[0], 1)

        # check that state isn't shared between instances

        a2 = A()

        self.assertNotEqual(a.value, a2.value)

        # check that it behaves like a property when there's no instance

        self.assertIsInstance(A.value, cached_property)