roam/20210806111448-working_with_currencies.org

:PROPERTIES:
:ID:       36fa073d-4b34-4b2b-bf96-0994a44df61e
:END:
#+title: Working with currency units in Python

- https://simple.wikipedia.org/wiki/ISO_4217

An example of converting between sub-units and base units in [[id:cda9c620-fec5-4549-b979-22fc06819d77][Python]] as defined
in [[id:bb3ab7e4-8824-4c32-bc74-e5b900d6e4d1][ISO 4217: Currency Codes]].

#+begin_src python :exports both :eval no-export
  from decimal import Decimal

  import pint
  from iso_4217 import define_currency_units

  currency_units = define_currency_units(pint.UnitRegistry(non_int_type=Decimal))


  def to_base_units(currency: str, amount: int) -> Decimal:
      """Convert an amount in a currency's smallest denomination to its base.

      e.g. a USD value in its lowest denomination (cents) as 1999 would convert to
      19.99 (dollars).
      """
      subunit = currency_units[f'{currency.upper()}s']
      return (subunit * amount).to_base_units().magnitude


  return to_base_units('USD', 1999)
#+end_src

#+RESULTS:
: 19.99