在 Python 中将 class 实例属性设置为只读

Question

我正在尝试将我的一些模块包装到 classes 中并开始使用属性。

正在努力将这两个答案组合在一起：making instance attribute read-only and validating attributes。

我希望能够创建 DataFolder 的实例 class:

df = DataFolder(owner="me", path="/.data")

之后，我希望能够允许编辑 owner 属性，但不允许编辑 path 属性。我希望能够在初始化时（path 和 owner）和之后（但仅 owner）验证属性。

class DataFolder(object):
    _path = None

    #----------------------------------------------------------------------
    def __init__(self,owner,path):
        self.path = path
        self.owner = owner

    @property
    #----------------------------------------------------------------------
    def owner(self):
        return self._owner

    @owner.setter
    #----------------------------------------------------------------------
    def owner(self,owner_value):
        if "me" not in owner_value:
            raise Exception("invalid owner")
        self._owner = owner_value

    @property
    #----------------------------------------------------------------------
    def path(self):
        return self._path

    @path.setter
    #----------------------------------------------------------------------
    def path(self,path_value):
        if self._path is not None:
            raise AttributeError("Cannot edit path of existing data folder")
        if "dat" not in path_value:
            raise Exception("invalid folder")
        self._path = path_value

是不是correct/best使用全局变量_path = None并检查@path.setter中的if self._path is not None:？代码运行正常，但我想知道是否有更好的方法。

Answer 1

我觉得不错，除了一件事：_path = None 属于 class。

这只是一个小改进：

class DataFolder(object):
    def __init__(self, owner, path):
        self._path = None  # now it is an instance variable.
        self.path = path
        self.owner = owner

    @property
    def owner(self):
        return self._owner

    def _validate_owner(self, owner_value):
        if "me" not in owner_value:
            raise ValueError("invalid owner")

    @owner.setter
    def owner(self, owner_value):
        self._validate_owner(owner_value)
        self._owner = owner_value

    @property
    def path(self):
        return self._path

    def _validate_path(self, path_value):
        if self._path is not None:
            raise AttributeError("Cannot edit path of existing data folder")
        if "dat" not in path_value:
            raise ValueError("invalid folder")

    @path.setter
    def path(self, path_value):
        self._validate_path(path_value)
        self._path = path_value

使用：

d = DataFolder('me', 'data')
print(d.path, d.owner)
d.path = 'new_data'

输出：

('data', 'me')
new_me
AttributeError: Cannot edit path of existing data folder

在 Python 中将 class 实例属性设置为只读

Make a class instance attribute read-only in Python

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