[pysqlite] [APSW 3.6.3-r1] cursor.execute only runs once?

Hello

I'm not a Python expert, and lost as to why APSW only runs the INSERT 
once and then exits the loop although there are more records to be 
read from the SELECT:

========
import urllib
import re
import apsw

url = 
"http://www.amazon.com/s/ref=nb_ss_gw?url=search-alias%3Daps&field-keywords="
pattern = 'class="srTitle">(.+?)</span>'

connection=apsw.Connection("mybooks.sqlite")
cursor=connection.cursor()

p = re.compile(pattern)

for row in cursor.execute("SELECT isbn FROM books WHERE title IS NULL"):
	if row[0]:
		isbn = row[0]

		f = urllib.urlopen(url + isbn)
		page = f.read()
		f.close()
		
		m=p.search(page,re.I | re.S | re.M)
		if m:
			print "Found ISBN " + isbn + " = " + m.group(1)
			sql = "UPDATE books SET title='%s' WHERE isbn='%s'" % (m.group(1),isbn)

			#Why does it end after updating just one record?
			try:
				cursor.execute(sql)
			except:
				print "Error"
		else:
			print "Nothing found for ISBN " + isbn

connection.close(True)
========

Any idea? Thank you.