FIX: to_sql dtype argument accepting SQLAlchemy type instance (GH9083)

doc/source/whatsnew/v0.16.0.txt

@@ -60,7 +60,8 @@ Bug Fixes
 
 - Fixed bug in ``to_sql`` when mapping a Timestamp object column (datetime
   column with timezone info) to the according sqlalchemy type (:issue:`9085`).
-
+- Fixed bug in ``to_sql`` ``dtype`` argument not accepting an instantiated
+  SQLAlchemy type  (:issue:`9083`).
 
 
 

pandas/io/sql.py

@@ -1159,9 +1159,9 @@ def to_sql(self, frame, name, if_exists='fail', index=True,
 
         """
         if dtype is not None:
-            import sqlalchemy.sql.type_api as type_api
+            from sqlalchemy.types import to_instance, TypeEngine
             for col, my_type in dtype.items():
-                if not issubclass(my_type, type_api.TypeEngine):
+                if not isinstance(to_instance(my_type), TypeEngine):
                     raise ValueError('The type of %s is not a SQLAlchemy '
                                      'type ' % col)
 

pandas/io/tests/test_sql.py

@@ -1229,6 +1229,14 @@ def test_dtype(self):
         self.assertRaises(ValueError, df.to_sql,
                           'error', self.conn, dtype={'B': str})
 
+        # GH9083
+        df.to_sql('dtype_test3', self.conn, dtype={'B': sqlalchemy.String(10)})
+        meta.reflect()
+        sqltype = meta.tables['dtype_test3'].columns['B'].type
+        print(sqltype)
+        self.assertTrue(isinstance(sqltype, sqlalchemy.String))
+        self.assertEqual(sqltype.length, 10)
+
     def test_notnull_dtype(self):
         cols = {'Bool': Series([True,None]),
                 'Date': Series([datetime(2012, 5, 1), None]),