在类属性更改时调用Python方法

Question

我正在编写一个API解析Twitter机器人，对OOP来说是个新手。我有一些依赖于全局变量的现有Python代码，并认为我可以借此机会学习。

我有以下Team类，这些类在解析API时会更新，并且希望在类属性更改时能够调用完全不相关的（外部）方法。

class Team(object):
  def __init__(self, team_name, tri_code, goals, shots, goalie_pulled):
    self.team_name = team_name
    self.tri_code = tri_code
    self.goals = goals
    self.shots = shots
    self.goalie_pulled = goalie_pulled

goalie_pulled对于现有实例，何时更改，Team我希望调用以下方法（伪代码）：

def goalie_pulled_tweet(team):
  tweet = "{} has pulled their goalie with {} remaining!".format(team.team_name, game.period_remain)
  send_tweet(tweet)

两件事情 -

1. 一旦检测到属性已更改，如何goalie_pulled_tweet从Team班级内部调用goalie_pulled？
2. 我可以Game从任何地方访问对象的实例，还是也需要将其传递给该变量？

Answer 1

您应该看看属性类。基本上，它使您可以封装行为和私有成员，而消费者甚至不会注意到它。

在您的示例中，您可能具有以下goalie_pulled属性：

class Team(object):
    def __init__(self, team_name, tri_code, goals, shots, goalie_pulled):
        # Notice the identation here. This is very important.
        self.team_name = team_name
        self.tri_code = tri_code
        self.goals = goals
        self.shots = shots

        # Prefix your field with an underscore, this is Python standard way for defining private members
        self._goalie_pulled = goalie_pulled

    @property
    def goalie_pulled(self):
        return self._goalie_pulled

    @goalie_pulled.setter
    def goalie_pulled(self, new_value):
        self._goalie_pulled = new_value
        goalie_pulled_tweet(self) #self is the current Team instance

从消费者的角度来看：

team = create_team_instance()

# goalie_pulled_tweet is called
team.goalie_pulled = 'some_value'

我建议您尽可能（且必须）使用属性，因为它们是一种很好的抽象方法。