import sqlite3

class Point(object):

    def __init__(self, x, y):

        self.x, self.y = x, y

    def __conform__(self, protocol):

        if protocol is sqlite3.PrepareProtocol:

            return "%f;%f" % (self.x, self.y)

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

cur = con.cursor()

p = Point(4.0, -3.2)

cur.execute("select ?", (p,))

print cur.fetchone()[0]