Q. I'm writing a fixed-point application to two decimal places. Some inputs have many places and needed to be rounded. Others are not supposed to have excess digits and need to be validated. What methods should I use?
A. The quantize() method rounds to a fixed number of decimal places. If the Inexact trap is set, it is also useful for validation:
TWOPLACES = Decimal(10) ** -2 # Round to two places Decimal("3.214").quantize(TWOPLACES) Decimal("3.21") # Validate that a number does not exceed two places Decimal("3.21").quantize(TWOPLACES, context=Context(traps=[Inexact])) Decimal("3.21")
I think an example of what happens when it does exceed two places would make this example clearer. For example, adding this to the end of that:
Decimal("3.214").quantize(TWOPLACES, context=Context(traps=[Inexact])) Traceback (most recent call last): [...] Inexact: Changed in rounding
=Tony.Meyer