1 import sqlite3

     2 

     3 class MySum:

     4     def __init__(self):

     5         self.count = 0

     6 

     7     def step(self, value):

     8         self.count += value

     9 

    10     def finalize(self):

    11         return self.count

    12 

    13 con = sqlite3.connect(":memory:")

    14 con.create_aggregate("mysum", 1, MySum)

    15 cur = con.cursor()

    16 cur.execute("create table test(i)")

    17 cur.execute("insert into test(i) values (1)")

    18 cur.execute("insert into test(i) values (2)")

    19 cur.execute("select mysum(i) from test")

    20 print cur.fetchone()[0]