#!/usr/bin/env python
     # encoding: utf-8
     #
     # Copyright (c) 2010 Doug Hellmann.  All rights reserved.
     #
     """Sorting a custom type.
     """
     #end_pymotw_header
     
     import sqlite3
     try:
         import cPickle as pickle
     except:
         import pickle
     
     db_filename = 'todo.db'
     
     def adapter_func(obj):
         return pickle.dumps(obj)
     
     def converter_func(data):
         return pickle.loads(data)
     
     class MyObj(object):
         def __init__(self, arg):
             self.arg = arg
         def __str__(self):
             return 'MyObj(%r)' % self.arg
         def __cmp__(self, other):
             return cmp(self.arg, other.arg)
     
     # Register the functions for manipulating the type.
     sqlite3.register_adapter(MyObj, adapter_func)
     sqlite3.register_converter("MyObj", converter_func)
     
     def collation_func(a, b):
         a_obj = converter_func(a)
         b_obj = converter_func(b)
         print 'collation_func(%s, %s)' % (a_obj, b_obj)
         return cmp(a_obj, b_obj)
     
     with sqlite3.connect(db_filename, detect_types=sqlite3.PARSE_DECLTYPES) as conn:
         # Define the collation
         conn.create_collation('unpickle', collation_func)
     
         # Clear the table and insert new values
         conn.execute('delete from obj')
         conn.executemany('insert into obj (data) values (?)',
                          [(MyObj(x),) for x in xrange(5, 0, -1)],
                          )
     
         # Query the database for the objects just saved
         print '\nQuerying:'
         cursor = conn.cursor()
         cursor.execute("select id, data from obj order by data collate unpickle")
         for obj_id, obj in cursor.fetchall():
             print obj_id, obj
             print