class ReactNumber

gistfile1.txt

class ReactNumber(Observerble, Observer):
    def __init__(self, number: Union[int, float, Strategy]):
        super().__init__(number)
        self.value = number

    @property
    def value(self) -> Union[int, float]:
        if self._number is None and self._strategy is not None:
            self._number = self._strategy.eval()
        return self._number

    @value.setter
    def value(self, new_value: Union[int, float, Strategy]) -> None:
        self._number = None
        self._strategy = None
        if isinstance(new_value, Strategy):
            self._strategy = new_value
        else:
            self._number = new_value
        self.notify()

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

    def __repr__(self) -> str:
        return str(self)

    def update(self, *args, **kwargs) -> None:
        if self._strategy is not None:
            self._number = self._strategy.eval()
        self.notify()

    def notify(self) -> None:
        for observer in self._observers_list:
            if hasattr(observer, 'update'):
                observer.update(self)

    def __mul__(self, other) -> 'ReactNumber':
        """
         Функция умножения
        :param other: другой объект
        :return: возвращает новое число
        """
        new_number = ReactNumber(MultiplicationStrategy(self, other))
        self.attach(new_number)
        if isinstance(other, ReactNumber):
            other.attach(new_number)
        return new_number

    def __rmul__(self, other) -> 'ReactNumber':
        """
        Функция отражённое умножение
        :param other: другой объект
        :return: возвращает новое число
        """
        new_number = ReactNumber(MultiplicationStrategy(other, self))
        self.attach(new_number)
        if isinstance(other, ReactNumber):
            other.attach(new_number)
        return new_number

    def __add__(self, other) -> 'ReactNumber':
        """
        Функция сложения
        :param other: другой объект
        :return: возвращает новое число
        """
        new_number = ReactNumber(SummatoryStrategy(self, other))
        self.attach(new_number)
        if isinstance(other, ReactNumber):
            other.attach(new_number)
        return new_number

    def __radd__(self, other) -> 'ReactNumber':
        """
        Функция отражённое сложение
        :param other: другой объект
        :return: возвращает новое число
        """
        new_number = ReactNumber(SummatoryStrategy(other, self))
        self.attach(new_number)
        if isinstance(other, ReactNumber):
            other.attach(new_number)
        return new_number

    def __sub__(self, other) -> 'ReactNumber':
        """
        Функция вычитания
        :param other: другой объект
        :return: возвращает новое число
        """
        new_number = ReactNumber(DifferenceStrategy(self, other))
        self.attach(new_number)
        if isinstance(other, ReactNumber):
            other.attach(new_number)
        return new_number

    def __rsub__(self, other) -> 'ReactNumber':
        """
        Функция отражённое вычитание
        :param other: другой объект
        :return: возвращает новое число
        """
        new_number = ReactNumber(DifferenceStrategy(self, other))
        self.attach(new_number)
        if isinstance(other, ReactNumber):
            other.attach(new_number)
        return new_number * -1