remove "is None" from boolean tests

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index bec5d5c6ee193a0b2b51828613503d4cb41b7a79..7cec88e30ca771247075127d9f6f3d70607f041a 100644 (file)
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -1281,9 +1281,9 @@ class Mapper(object):
             if ret is not EXT_CONTINUE:
                 row = ret
 
-        if not refresh_instance and not skip_polymorphic and self.polymorphic_on is not None:
+        if not refresh_instance and not skip_polymorphic and self.polymorphic_on:
             discriminator = row[self.polymorphic_on]
-            if discriminator is not None:
+            if discriminator:
                 mapper = self.polymorphic_map[discriminator]
                 if mapper is not self:
                     if ('polymorphic_fetch', mapper) not in context.attributes: