That definitely looks like it should work according to the book.
What do you get when you do it exactly like the book?
>>> db.define_table('item',
Field
<http://web2py.com/book/default/docstring/Field>('unit_price','double'),
Field
<http://web2py.com/book/default/docstring/Field>('quantity','integer'),
Field <http://web2py.com/book/default/docstring/Field>('total_price',
compute=lambda r: r['unit_price']*r['quantity']))
>>> r = db.item.insert(unit_price=1.99, quantity=5)
>>> print r.total_price
What version of Web2py? Do you get different behavior if you pull the
compute out of the table def?
db.item.total_price.compute = lambda r: r['unit_price']*r['quantity']
How about:
db.item.total_price.compute = lambda r: float(r['unit_price']) *
float(r['quantity'])
