Implementacja klasy Money w Pythonie

Question

Witam

Co sądzicie o takiej implementacji klasy Money?

import functools
from decimal import Decimal
from dataclasses import dataclass


@dataclass
class Currency:
    name: str
    symbol: str
    exchange_rate: Decimal

    def __str__(self) -> str:
        return self.name

    def __repr__(self) -> str:
        return f"{self.__class__.__name__}({self.name!r}, {self.symbol!r}, {self.exchange_rate!r})"


@functools.total_ordering
class Money:
    def __init__(self, amount: Decimal, currency: Currency, precision: int = 2):
        self._amount = amount
        self.precision = precision
        self.currency = currency

    @property
    def amount(self) -> Decimal:
        return self._amount.quantize(Decimal("10") ** -self.precision)

    @amount.setter
    def amount(self, value: Decimal) -> None:
        self._amount = value

    def __str__(self) -> str:
        return f"{self.amount} {self.currency.symbol}"

    def __repr__(self) -> str:
        return f"{self.__class__.__name__}({self.amount!r}, {self.currency!r})"

    def __add__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot add two {self.__class__.__name__} instances: "
                             "different currency property")
        return Money(self.amount + other.amount, self.currency)

    def __sub__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot subtract two {self.__class__.__name__} instances: "
                             "different currency property")
        return Money(self.amount - other.amount, self.currency)

    def __mul__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot multiply two {self.__class__.__name__} instances: "
                             "different currency property")
        return Money(self.amount * other.amount, self.currency, self.precision)

    def __truediv__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot divide two {self.__class__.__name__} instances: "
                             "different currency property")
        return Money(self.amount / other.amount, self.currency, self.precision)

    def __iadd__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot add two {self.__class__.__name__} instances: "
                             "different currency property")
        self.amount += other.amount
        return self

    def __isub__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot subtract two {self.__class__.__name__} instances: "
                             "different currency property")
        self.amount -= other.amount
        return self

    def __imul__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot multiply two {self.__class__.__name__} instances: "
                             "different currency property")
        self.amount *= other.amount
        return self

    def __idiv__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot divide two {self.__class__.__name__} instances: "
                             "different currency property")
        self.amount /= other.amount
        return self

    def __lt__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot compare two {self.__class__.__name__} instances: "
                             "different currency property")
        return self.amount < other.amount

    def __eq__(self, other):
        if self.currency != other.currency:
            raise ValueError(f"cannot compare two {self.__class__.__name__} instances: "
                             "different currency property")
        return self.amount == other.amount

Testy:

import pytest
from example_shop.shop.money import Currency, Money
from decimal import Decimal
from typing import Optional


def money_euro(amount: str, precision: Optional[int] = None) -> Money:
    if precision is None:
        return Money(Decimal(amount), Currency("Euro", "EUR", Decimal("4.52")))
    return Money(Decimal(amount), Currency("Euro", "EUR", Decimal("4.52")), precision)


def money_usd(amount: str, precision: Optional[int] = None) -> Money:
    if precision is None:
        return Money(Decimal(amount), Currency("American dollar", "USD", Decimal("4.17")))
    return Money(Decimal(amount), Currency("American dollar", "USD", Decimal("4.17")), precision)


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("2.7")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("4.0")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("4.00000")),
                          (money_usd("1.5", 4), money_usd("1.5", 3), money_usd("3", 4)),
                          (money_usd("-1.5", 4), money_usd("3", 5), money_usd("1.5", 5))])
def test_money_add_the_same_currency(price1, price2, expected):
    assert price1 + price2 == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("0.3")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("1.4")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("1.40000")),
                          (money_usd("1.5", 4), money_usd("1.5", 3), money_usd("0", 4)),
                          (money_usd("1.5", 4), money_usd("3", 5), money_usd("-1.5", 5))])
def test_money_subtract_the_same_currency(price1, price2, expected):
    assert price1 - price2 == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("1.8")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("3.51")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("3.51000")),
                          (money_usd("0", 4), money_usd("1.5", 3), money_usd("0", 4)),
                          (money_usd("1.5", 4), money_usd("-3", 5), money_usd("-4.5", 5))])
def test_money_multiply_the_same_currency(price1, price2, expected):
    assert price1 * price2 == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("1.25")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("2.08")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("2.08000")),
                          (money_usd("0", 4), money_usd("1.5", 3), money_usd("0", 4)),
                          (money_usd("1.5", 4), money_usd("-3", 5), money_usd("-0.5", 5))])
def test_money_divide_the_same_currency(price1, price2, expected):
    assert price1 / price2 == expected


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_add_the_different_currency(price1, price2):
    with pytest.raises(ValueError):
        assert price1 + price2


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_subtract_different_currency(price1, price2):
    with pytest.raises(ValueError):
        assert price1 - price2


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_multiply_different_currency(price1, price2):
    with pytest.raises(ValueError):
        assert price1 * price2


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_divide_different_currency(price1, price2):
    with pytest.raises(ValueError):
        assert price1 / price2


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("2.7")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("4.0")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("4.00000")),
                          (money_usd("1.5", 4), money_usd("1.5", 3), money_usd("3", 4)),
                          (money_usd("-1.5", 4), money_usd("3", 5), money_usd("1.5", 5))])
def test_money_add_in_place_the_same_currency(price1, price2, expected):
    result = price1
    result += price2
    assert result == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("0.3")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("1.4")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("1.40000")),
                          (money_usd("1.5", 4), money_usd("1.5", 3), money_usd("0", 4)),
                          (money_usd("1.5", 4), money_usd("3", 5), money_usd("-1.5", 5))])
def test_money_subtract_in_place_the_same_currency(price1, price2, expected):
    result = price1
    result -= price2
    assert result == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("1.8")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("3.51")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("3.51000")),
                          (money_usd("0", 4), money_usd("1.5", 3), money_usd("0", 4)),
                          (money_usd("1.5", 4), money_usd("-3", 5), money_usd("-4.5", 5))])
def test_money_multiply_in_place_the_same_currency(price1, price2, expected):
    result = price1
    result *= price2
    assert result == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_usd("1.5"), money_usd("1.2"), money_usd("1.25")),
                          (money_usd("2.7"), money_usd("1.3"), money_usd("2.08")),
                          (money_usd("2.700"), money_usd("1.3"), money_usd("2.08000")),
                          (money_usd("0", 4), money_usd("1.5", 3), money_usd("0", 4)),
                          (money_usd("1.5", 4), money_usd("-3", 5), money_usd("-0.5", 5))])
def test_money_divide_in_place_the_same_currency(price1, price2, expected):
    result = price1
    result /= price2
    assert result == expected


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_add_in_place_the_different_currency(price1, price2):
    with pytest.raises(ValueError):
        result = price1
        result += price2
        assert result


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_subtract_in_place_different_currency(price1, price2):
    with pytest.raises(ValueError):
        result = price1
        result -= price2
        assert result


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_multiply_in_place_different_currency(price1, price2):
    with pytest.raises(ValueError):
        result = price1
        result *= price2
        assert result


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.5"), money_euro("1.2")),
                          (money_euro("1.2"), money_usd("1.5")),
                          (money_usd("1.5", 4), money_euro("1.2", 5)),
                          (money_euro("1.2", 4), money_usd("1.5", 5))])
def test_money_divide_in_place_different_currency(price1, price2):
    with pytest.raises(ValueError):
        result = price1
        result /= price2
        assert result

@pytest.mark.parametrize("price1,price2,expected",
                         [(money_euro("1.23"), money_euro("4.56"), True),
                          (money_euro("1.5"), money_euro("1"), False),
                          (money_usd("-2"), money_usd("0"), True),
                          (money_euro("0"), money_euro("0"), False)])
def test_less_than_the_same_currency(price1, price2, expected):
    assert (price1 < price2) == expected


@pytest.mark.parametrize("price1,price2,expected",
                         [(money_euro("1.23"), money_euro("4.56"), False),
                          (money_euro("1.5"), money_euro("1"), False),
                          (money_usd("-2"), money_usd("0"), False),
                          (money_euro("0"), money_euro("0"), True)])
def test_equal_the_same_currency(price1, price2, expected):
    assert (price1 == price2) == expected


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.23"), money_euro("4.56")),
                          (money_euro("1.5"), money_usd("1"))])
def test_less_than_different_currency(price1, price2):
    with pytest.raises(ValueError):
        assert price1 < price2


@pytest.mark.parametrize("price1,price2",
                         [(money_usd("1.23"), money_euro("4.56")),
                          (money_euro("1.5"), money_usd("1"))])
def test_equal_different_currency(price1, price2):
    with pytest.raises(ValueError):
        assert price1 == price2

Czy uzależnianie od siebie kolejności przypisań jest ok?

Z góry dziękuję i pozdrawiam :-)