Added naturally_equivalent utility function

sqlalchemy_utils/functions/__init__.py

@@ -210,6 +210,26 @@ def identity(obj):
     return tuple(id_)
 
 
+def naturally_equivalent(obj, obj2):
+    """
+    Returns whether or not two given SQLAlchemy declarative instances are
+    naturally equivalent (all their non primary key properties are equivalent).
+
+    :param obj: SQLAlchemy declarative model object
+    :param obj2: SQLAlchemy declarative model object to compare with `obj`
+    """
+    for prop in sa.inspect(obj.__class__).iterate_properties:
+        if not isinstance(prop, sa.orm.ColumnProperty):
+            continue
+
+        if prop.columns[0].primary_key:
+            continue
+
+        if not (getattr(obj, prop.key) == getattr(obj2, prop.key)):
+            return False
+    return True
+
+
 def render_statement(statement, bind=None):
     """
     Generate an SQL expression string with bound parameters rendered inline

tests/test_utility_functions.py

@@ -1,5 +1,6 @@
 import sqlalchemy as sa
-from sqlalchemy_utils import escape_like, defer_except
+from sqlalchemy_utils import escape_like
+from sqlalchemy_utils.functions import naturally_equivalent
 from tests import TestCase
 from sqlalchemy_utils.functions import (
     non_indexed_foreign_keys,
@@ -12,6 +13,18 @@ class TestEscapeLike(TestCase):
         assert escape_like('_*%') == '*_***%'
 
 
+class TestNaturallyEquivalent(TestCase):
+    def test_returns_true_when_properties_match(self):
+        assert naturally_equivalent(
+            self.User(name=u'someone'), self.User(name=u'someone')
+        )
+
+    def test_skips_primary_keys(self):
+        assert naturally_equivalent(
+            self.User(id=1, name=u'someone'), self.User(id=2, name=u'someone')
+        )
+
+
 class TestFindNonIndexedForeignKeys(TestCase):
     # dns = 'postgres://postgres@localhost/sqlalchemy_utils_test'