gistfile1.txt

diff --git a/django_root/django/db/models/base.py b/django_root/django/db/models/base.py
index 37331b3..4da2802 100644
--- a/django_root/django/db/models/base.py
+++ b/django_root/django/db/models/base.py
@@ -5,6 +5,7 @@ from itertools import izip
 import django.db.models.manager     # Imported to register signal handler.
 from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned, FieldError, ValidationError, NON_FIELD_ERRORS
 from django.core import validators
+from django.db.models.expressions import ExpressionNode
 from django.db.models.fields import AutoField, FieldDoesNotExist
 from django.db.models.fields.related import OneToOneRel, ManyToOneRel, OneToOneField
 from django.db.models.query import delete_objects, Q
@@ -436,6 +437,20 @@ class Model(object):
 
     save.alters_data = True
 
+    def update(self, using=None, **kwargs):
+        """
+        Updates specified attributes on the current instance.
+        """
+        assert self.pk, "Cannot update an instance that has not yet been created."
+        self.__class__._base_manager.using(using).filter(pk=self.pk).update(**kwargs)
+        for k, v in kwargs.iteritems():
+            if isinstance(v, ExpressionNode):
+                # NotImplemented
+                continue
+            setattr(self, k, v)
+
+    update.alters_data = True
+
     def save_base(self, raw=False, cls=None, origin=None, force_insert=False,
             force_update=False, using=None):
         """
diff --git a/django_root/tests/modeltests/update/tests.py b/django_root/tests/modeltests/update/tests.py
index 05397f8..ea7259e 100644
--- a/django_root/tests/modeltests/update/tests.py
+++ b/django_root/tests/modeltests/update/tests.py
@@ -1,4 +1,5 @@
 from django.test import TestCase
+from django.db.models import F
 
 from models import A, B, D
 
@@ -47,3 +48,17 @@ class SimpleTest(TestCase):
         self.failUnlessEqual(num_updated, 0)
         cnt = D.objects.filter(y=100).count()
         self.failUnlessEqual(cnt, 0)
+    
+    def test_self_update(self):
+        """
+        Test the update method attached to an instance.
+        """
+        self.a1.update(x=100)
+        self.failUnlessEqual(self.a1.x, 100)
+    
+    def test_self_update_with_expressions(self):
+        """
+        Test the update method with expressions which are not implemented.
+        """
+        self.a1.update(x=F('x') + 100)
+        self.failUnlessEqual(self.a1.x, 10)
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