Further examples:
quantity = 20.5
unit_cost = Decimal('2.99')
total_cost = Decimal(str(quantity)) * unit_cost
Or using the the example you provided above:
if ((form.vars.drops * form.vars.price_change) / form.vars.start_price) <
0.20
Assuming that form.vars.drops is a float, and form.vars.price_change and
form.vars.start_price are both Decimals:
if ((Decimal(str(form.vars.drops)) * form.vars.price_change) /
form.vars.start_price) < Decimal('0.20')
Mixing floats and Decimals is frustrating, so I always try to make anything
(like a quantity field) that requires math with price fields a decimal as
well:
db.define_table('order',
Field('order_number', length=10),
Field('quantity', 'decimal(10,2)'),
Field('unit_price', 'decimal(10,2)')
)
Then a calculation like this is easy:
total_price = order.quantity * order.unit_price
