Is there a faster alternative to python's Decimal?

Question

Does anyone know of a faster decimal implementation in python?

As the example below demonstrates, the standard library\'s decimal module is ~100 times slower than

Answer 1

You should compare Decimal to Long Integer performance, not floating point. Floating point is mostly hardware these days. Decimal is used for decimal precision, while Floating Point is for wider range. Use the decimal package for monetary calculations.

To quote the decimal package manual:

Decimal numbers can be represented exactly. In contrast, numbers like 1.1 do not have an exact representation in binary floating point. End users typically would not expect 1.1 to display as 1.1000000000000001 as it does with binary floating point.

The exactness carries over into arithmetic. In decimal floating point, "0.1 + 0.1 + 0.1 - 0.3" is exactly equal to zero. In binary floating point, result is 5.5511151231257827e-017. While near to zero, the differences prevent reliable equality testing and differences can accumulate. For this reason, decimal would be preferred in accounting applications which have strict equality invariants.