Relative speed of various methods of coercion from int to real in sqlite3

test_cast.py

#!/usr/bin/env python

import sqlite3
from random import choice
from timeit import timeit
from itertools import chain

con = sqlite3.connect('test_cast.db', isolation_level=None)  # autocommit
cur = con.cursor()

cur.execute('drop table if exists tab')
cur.execute('create table tab (a integer, b integer, c real)')
ints = range(500)

nullrows = ((None, None), (None, 1), (1, None))
randomints = ((choice(ints), choice(ints)) for i in xrange(1000))
cur.executemany('insert into tab (a, b) values (?, ?)',
                chain(nullrows, randomints))
con.close()

setup = """\
import sqlite3
con = sqlite3.connect('test_cast.db', isolation_level=None)  # autocommit
cur = con.cursor()
"""

cmd = "cur.execute('update tab set c = a*1.0/b')"
print cmd
print timeit(cmd, setup=setup, number=1000)
cmd = "cur.execute('update tab set c = cast(a as real)/b')"
print cmd
print timeit(cmd, setup=setup, number=1000)