Development of billing system with Django framework | Hacker News Reader

Development of billing system with Django framework

blog.bitcalm.com

9 pointsborisdus5 comments

Money should be represented in the base unit, for dollars that is cents. So for your sum fields it should be sum_in_base_units = 859 not 8.59. Decimal can lose accuracy as you move around systems, it's most safe to just use base units.

> Decimal can lose accuracy as you move around systems

Could you please provide an example? Given that Decimals are simplistically represented as a tuple (sign, digits, exponent), I don't see how it's less accurate than an int.

Simplest one: open up Python, enter:

    ((.1)*3)/3

It should come up as 0.10000000000000002. I honestly don't understand the reason, though.

You're thinking of floats which are different than the Decimal type[1].

https://docs.python.org/3/library/decimal.html?highlight=dec...

These are normal floats, not Decimals, which are Python's exact floating point type.

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