Using Decimal.quantize

Links

• decimal — Decimal fixed point and floating point arithmetic — Python 3.12.4 documentation

quantize

From the docs:

The quantize() method rounds a number to a fixed exponent. This method is useful for monetary applications that often round results to a fixed number of places:

from decimal import Decimal

Decimal('7.325').quantize(Decimal('.01'), rounding=ROUND_DOWN)
Decimal('7.32')

Decimal('7.325').quantize(Decimal('1.'), rounding=ROUND_UP)
Decimal('8')

Notes

You have to call quantize on a Decimal object. You also pass it another Decimal object. The number of decimal places in the Decimal you pass to quantize determines the number of decimal places in your result.

To use this with money, you might have something like:

>>> from decimal import Decimal
>>> Decimal(1989)
Decimal('1989')
>>> Decimal(1989).quantize(Decimal("00"))
Decimal('1989')
>>> Decimal(1989).quantize(Decimal(".00"))
Decimal('1989.00')
>>> Decimal(19.89).quantize(Decimal(".00"))
Decimal('19.89')
>>> Decimal(19.89).quantize(Decimal(".013"))
Decimal('19.890')

I don't love working with Decimals. But needs must, and discovering quantize was nice.