python - 为什么我的类实例是 int 类型(我无法访问它的属性)？

Question

我在Python中创建了一个只有抽象方法的类，然后实现了BasicMR类中的所有方法(并非BasicMR的所有代码都存在于代码片段，但在 self.generate_positions() 内部调用方法 test_stationary()):

class Strategy(object):
    __metaclass__=ABCMeta

    @abstractmethod
    def generate_positions(self):
        raise NotImplementedError("You must implement generatePositions()!")

    @abstractmethod
    def get_positions(self):
        raise NotImplementedError("You must implement getPositions()!")


class BasicMR(Strategy):
    def __init__(self, security, lookback=30):
        self.__securities = []
        self.__securities = security   # it could be either one security or a list of security objects
        self.__positions = self.generate_positions()

    def test_stationary(self, lb=30):
        if not isinstance(self.__securities, list):
            securities = [self.__securities]
        else:
            securities = self.__securities
        prices = [one_stock.get_prices(lb) for one_stock in securities]  # list comprehension
        results = [ts.adfuller(price_series, regression="c", autolag='AIC') for price_series in prices]
        simple_results = [BasicMR.simplify_adf_results(result[1], result[0], result[4]) for result in results]
        if len(simple_results) == 1:
            return simple_results[0]
        else:
            return simple_results

    def generate_positions(self, long_only=False, time_frame=20, max_holding_period = 20):
        result = []
        names = []
        # HERE IS SOME CODE
        return [names, result]

    def get_positions(self):
        return self.__positions

但是，当我创建 BasicMR() 实例时，我在这一行收到错误:

if not isinstance(self.__securities, list):

错误:

AttributeError: 'int' object has no attribute '_BasicMR__securities'

不知何故，我的 BasicMR 类实例被识别为 int 类型，并且我不知道如何处理该错误。

Answer 1

您正在类里面调用 test_stationary :

>>> BasicMR.test_stationary(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 20, in test_stationary
AttributeError: 'int' object has no attribute '_BasicMR__securities'

这会传入 42 作为 self 参数，因为该方法未绑定(bind)。

您无法创建该类的实例，因为您没有提供 generate_positions 和 get_positions 的具体实现:

>>> BasicMR([])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 17, in __init__
  File "<string>", line 6, in generate_positions
NotImplementedError: You must implement generatePositions()!