What class to use for money representation?

python currency rounding-error arbitrary-precision precision
Esteban Küber picture Esteban Küber · Sep 10, 2009 · Viewed 26.7k times · Source

What class should I use for representation of money to avoid most rounding errors?

Should I use Decimal, or a simple built-in number?

Is there any existing Money class with support for currency conversion that I could use?

Any pitfalls that I should avoid?

Answer

Thiago Chaves picture Thiago Chaves · Jul 23, 2012

Never use a floating point number to represent money. Floating numbers do not represent numbers in decimal notation accurately. You would end with a nightmare of compound rounding errors, and unable to reliably convert between currencies. See Martin Fowler's short essay on the subject.

If you decide to write your own class, I recommend basing it on the decimal data type.

I don't think python-money is a good option, because it wasn't maintained for quite some time and its source code has some strange and useless code, and exchanging currencies is simply broken.

Try py-moneyed. It's an improvement over python-money.

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