Question

我正在尝试将凭证类下的self.role设置为使用AXL类下的self.role。想法是根据api的角色来设置不同的类。如果axl类仅读取数据，则角色将为r。

PATH = 'home_drive_'
PLATFORM = 'Linux_'
ITEM = '_PC'

class Credential:

    def __init__(self, path, platform):
        self.role = 'rx'
        self.username_file = path + platform + ('The role should be the same as AXL role: ' + self.role)

class AXL(Credential):

    def __init__(self, path, platform, item):
        super().__init__(path, platform)
        self.role = 'r'
        self.item = item

    def final(self):
        return self.username_file + self.item

reg1 = AXL(PATH, PLATFORM, ITEM)

print('AXL role:', reg1.role)
print(reg1.username_file)
print(reg1.final())

结果将是

AXL role: r 
home_drive_Linux_The role should be the same as AXL role: rx 
home_drive_Linux_The role should be the same as AXL role: rx_PC

代替rx，我需要看r

这是沙箱中的link

Answer 1

Answer by @chepner绝对是正确的解决方案。我将其保留在这里，是为了过分复杂的简单问题。

您可以在username_file上将Credential设为@property，以便根据访问权限（而不是实例创建）对其进行评估。

class Credential:
    def __init__(self, path, platform):
        self.role = 'rx'
        self.path = path
        self.platform = platform

    @property
    def username_file(self):
        return self.path + self.platform + self.role

如果是AXL实例，则滚动将为'r'，如果是Credential实例则为'rx'。

如果要简化，还可以缓存第一个属性访问的结果：

class Credential:
    def __init__(self, path, platform):
        self.role = 'rx'
        self.path = path
        self.platform = platform
        self._username_file = None

    @property
    def username_file(self):
        if not self._usernme_file:
            self._username_file = self.path + self.platform + self.role
        return self._username_file

Answer 2

role应该是Credential.__init__的参数，而不是硬编码的，尽管它可以具有基类的默认值。子类会将所需角色直接传递给super().__init__。（如果某些东西必须具有'rx'的角色，那么它们也应该是Credential的子类，而不是Credential本身。）

class Credential:

    def __init__(self, path, platform, role='rx'):
        self.role = role
        self.username_file = path + platform + ('The role should be the same as AXL role: ' + role)


# class SomethingNeedingRoleRX(Credential):
#      def __init__(self, path, platform):
#          super().__init__(path, platform, 'rx')


class AXL(Credential):

    def __init__(self, path, platform, item):
        super().__init__(path, platform, 'r')
        self.item = item

    def final(self):
        return self.username_file + self.item

要更好地使用super，您可以考虑为__init__使用仅关键字的参数：

class Credential:
    def __init__(self, *, path, platform, role='rx', **kwargs):
        super().__init__(**kwargs)
        self.role = role
        self.username_file = path + platform + role


class AXL(Credential):
    def __init__(self, *, item, **kwargs):
        super().__init__(role='r', **kwargs)
        self.item = item

    def final(self):
        return self.username_file + self.item


reg1 = AXL(path=PATH, platform=PLATFORM, item=ITEM)

Answer 3

好吧，这里的问题基本上是username_file的数据类型；它是在构造函数中创建的字符串，并且在组件运行时不会更新。有几种方法可以解决此问题，使用属性是一种很好而干净的方法：

PATH = 'home_drive_'
PLATFORM = 'Linux_'
ITEM = '_PC'


class Credential:
    def __init__(self, path, platform):
        self.path = path
        self.platform = platform
        self.role = 'rx'
        self.username_file = self.path + self.platform + ('The role should be the same as AXL role: ' + self.role)

    @property
    def role(self):
        return self._role

    @role.setter
    def role(self, new_role):
        self._role = new_role
        self.username_file = self.path + self.platform + ('The role should be the same as AXL role: ' + self.role)


class AXL(Credential):
    def __init__(self, path, platform, item):
        super().__init__(path, platform)
        self.role = 'r'
        self.item = item

    def final(self):
        return self.username_file + self.item


reg1 = AXL(PATH, PLATFORM, ITEM)

print('AXL role:', reg1.role)
print(reg1.username_file)
print(reg1.final())

编辑：

仅作简短说明，您几乎可以将任何变量都转换为属性，选择角色的原因是资源管理。从本质上讲，每次角色更改（在程序中一次）时，在setter中更新username_file所花费的资源要少于每次调用getter时添加字符串（慢操作）所花费的资源。当然，考虑到程序资源管理的规模，不应该成为交易的障碍，而应提及解释答案的逻辑。

在python的主类中使用subclass属性

3 个答案: