Add is_loaded utility function

CHANGES.rst

@@ -4,6 +4,12 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
+0.27.8 (2014-11-13)
+^^^^^^^^^^^^^^^^^^^
+
+- Added is_loaded utility function
+
+
 0.27.7 (2014-11-03)
 ^^^^^^^^^^^^^^^^^^^
 

docs/orm_helpers.rst

@@ -76,6 +76,12 @@ identity
 .. autofunction:: identity
 
 
+is_loaded
+^^^^^^^^^
+
+.. autofunction:: is_loaded
+
+
 make_order_by_deterministic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

sqlalchemy_utils/__init__.py

@@ -29,6 +29,7 @@ from .functions import (
     has_index,
     has_unique_index,
     identity,
+    is_loaded,
     merge_references,
     mock_engine,
     naturally_equivalent,
@@ -118,6 +119,7 @@ __all__ = (
     has_index,
     identity,
     instrumented_list,
+    is_loaded,
     merge_references,
     mock_engine,
     naturally_equivalent,

sqlalchemy_utils/functions/__init__.py

@@ -38,6 +38,7 @@ from .orm import (
     has_any_changes,
     has_changes,
     identity,
+    is_loaded,
     naturally_equivalent,
     quote,
     table_name,
@@ -65,6 +66,7 @@ __all__ = (
     'has_any_changes',
     'has_changes',
     'identity',
+    'is_loaded',
     'is_auto_assigned_date_column',
     'is_indexed_foreign_key',
     'make_order_by_deterministic',

sqlalchemy_utils/functions/orm.py

@@ -755,6 +755,39 @@ def has_any_changes(obj, columns):
     return any(has_changes(obj, column) for column in columns)
 
 
+def is_loaded(obj, prop):
+    """
+    Return whether or not given property of given object has been loaded.
+
+    ::
+
+        class Article(Base):
+            __tablename__ = 'article'
+            id = sa.Column(sa.Integer, primary_key=True)
+            name = sa.Column(sa.String)
+            content = sa.orm.deferred(sa.Column(sa.String))
+
+
+        article = session.query(Article).get(5)
+
+        # name gets loaded since its not a deferred property
+        assert is_loaded(article, 'name')
+
+        # content has not yet been loaded since its a deferred property
+        assert not is_loaded(article, 'content')
+
+
+    .. versionadded: 0.27.8
+
+    :param obj: SQLAlchemy declarative model object
+    :param prop: Name of the property or InstrumentedAttribute
+    """
+    return not isinstance(
+        getattr(sa.inspect(obj).attrs, prop).loaded_value,
+        sa.util.langhelpers._symbol
+    )
+
+
 def identity(obj_or_class):
     """
     Return the identity of given sqlalchemy declarative model class or instance

tests/functions/test_is_loaded.py

@@ -0,0 +1,25 @@
+import sqlalchemy as sa
+from sqlalchemy.ext.declarative import declarative_base
+
+from sqlalchemy_utils import is_loaded
+
+
+class TestIsLoaded(object):
+    def setup_method(self, method):
+        Base = declarative_base()
+
+        class Article(Base):
+            __tablename__ = 'article_translation'
+            id = sa.Column(sa.Integer, primary_key=True)
+            title = sa.orm.deferred(sa.Column(sa.String(100)))
+
+        self.Article = Article
+
+    def test_loaded_property(self):
+        article = self.Article(id=1)
+        assert is_loaded(article, 'id')
+
+    def test_unloaded_property(self):
+        article = self.Article(id=4)
+        assert not is_loaded(article, 'title')
+