Don't serialize money as a float

In the US (and afaik all non JPY, KRW currencies), we’re cursed with fractional currencies. We can pay $1.49 for a candy bar. So if we want to represent that in code, the obvious thing is to use floats

x = '1.49'

Great. Right? Right?

a = '0.10'
b = '0.20'
print(a+b)
# 0.30000000000000004

which is a mess. Floating point is a good system, but it doesn’t optimize for correctness when dealing with only 1/100ths. Instead, we should use integers and use the smallest denomination. Integer math is well understood and makes bugs more obvious.

print(5//3)
# 1

This is done at most leading financial institutions (but not the API I was just reading!). In practice, this is what it looks like:

Monite

Stripe