modernize some more examples

1 files changed, 53 insertions, 45 deletions

diff --git a/examples/nested_sets/nested_sets.py b/examples/nested_sets/nested_sets.py
index e35ea61c3..8225a09f2 100644
--- a/examples/nested_sets/nested_sets.py
+++ b/examples/nested_sets/nested_sets.py
@@ -6,47 +6,17 @@ http://www.intelligententerprise.com/001020/celko.jhtml
 
 from sqlalchemy import (create_engine, Column, Integer, String, select, case,
     func)
-from sqlalchemy.orm import sessionmaker, MapperExtension, aliased
+from sqlalchemy.orm import Session, aliased
 from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy import event
 
-engine = create_engine('sqlite://', echo=True)
 Base = declarative_base()
 
-class NestedSetExtension(MapperExtension):
-    def before_insert(self, mapper, connection, instance):
-        if not instance.parent:
-            instance.left = 1
-            instance.right = 2
-        else:
-            personnel = mapper.mapped_table
-            right_most_sibling = connection.scalar(
-                select([personnel.c.rgt]).where(personnel.c.emp==instance.parent.emp)
-            )
-
-            connection.execute(
-                personnel.update(personnel.c.rgt>=right_most_sibling).values(
-                    lft = case(
-                            [(personnel.c.lft>right_most_sibling, personnel.c.lft + 2)],
-                            else_ = personnel.c.lft
-                          ),
-                    rgt = case(
-                            [(personnel.c.rgt>=right_most_sibling, personnel.c.rgt + 2)],
-                            else_ = personnel.c.rgt
-                          )
-                )
-            )
-            instance.left = right_most_sibling
-            instance.right = right_most_sibling + 1
-
-    # before_update() would be needed to support moving of nodes
-    # after_delete() would be needed to support removal of nodes.
-    # [ticket:1172] needs to be implemented for deletion to work as well.
-
 class Employee(Base):
     __tablename__ = 'personnel'
     __mapper_args__ = {
-        'extension':NestedSetExtension(),
-        'batch':False  # allows extension to fire for each instance before going to the next.
+        'batch': False  # allows extension to fire for each
+                        # instance before going to the next.
     }
 
     parent = None
@@ -59,9 +29,44 @@ class Employee(Base):
     def __repr__(self):
         return "Employee(%s, %d, %d)" % (self.emp, self.left, self.right)
 
+@event.listens_for(Employee, "before_insert")
+def before_insert(mapper, connection, instance):
+    if not instance.parent:
+        instance.left = 1
+        instance.right = 2
+    else:
+        personnel = mapper.mapped_table
+        right_most_sibling = connection.scalar(
+            select([personnel.c.rgt]).
+                where(personnel.c.emp == instance.parent.emp)
+        )
+
+        connection.execute(
+            personnel.update(
+                personnel.c.rgt >= right_most_sibling).values(
+                    lft=case(
+                        [(personnel.c.lft > right_most_sibling,
+                            personnel.c.lft + 2)],
+                        else_=personnel.c.lft
+                    ),
+                    rgt=case(
+                        [(personnel.c.rgt >= right_most_sibling,
+                                personnel.c.rgt + 2)],
+                            else_=personnel.c.rgt
+                      )
+            )
+        )
+        instance.left = right_most_sibling
+        instance.right = right_most_sibling + 1
+
+    # before_update() would be needed to support moving of nodes
+    # after_delete() would be needed to support removal of nodes.
+
+engine = create_engine('sqlite://', echo=True)
+
 Base.metadata.create_all(engine)
 
-session = sessionmaker(bind=engine)()
+session = Session(bind=engine)
 
 albert = Employee(emp='Albert')
 bert = Employee(emp='Bert')
@@ -81,23 +86,26 @@ fred.parent = chuck
 session.add_all([albert, bert, chuck, donna, eddie, fred])
 session.commit()
 
-print session.query(Employee).all()
+print(session.query(Employee).all())
 
 # 1. Find an employee and all his/her supervisors, no matter how deep the tree.
 ealias = aliased(Employee)
-print session.query(Employee).\
+print(session.query(Employee).\
             filter(ealias.left.between(Employee.left, Employee.right)).\
-            filter(ealias.emp=='Eddie').all()
+            filter(ealias.emp == 'Eddie').all())
 
-#2. Find the employee and all his/her subordinates. (This query has a nice symmetry with the first query.)
-print session.query(Employee).\
+#2. Find the employee and all his/her subordinates.
+# (This query has a nice symmetry with the first query.)
+print(session.query(Employee).\
     filter(Employee.left.between(ealias.left, ealias.right)).\
-    filter(ealias.emp=='Chuck').all()
+    filter(ealias.emp == 'Chuck').all())
 
-#3. Find the level of each node, so you can print the tree as an indented listing.
-for indentation, employee in session.query(func.count(Employee.emp).label('indentation') - 1, ealias).\
+#3. Find the level of each node, so you can print the tree
+# as an indented listing.
+for indentation, employee in session.query(
+            func.count(Employee.emp).label('indentation') - 1, ealias).\
     filter(ealias.left.between(Employee.left, Employee.right)).\
     group_by(ealias.emp).\
-    order_by(ealias.left):
-    print "    " * indentation + str(employee)
+        order_by(ealias.left):
+    print("    " * indentation + str(employee))