从配置文件创建具有属性的类

Question

我正试图从配置文件中动态创建一个Python类(为了简单起见，我在示例中使用了字典(。我创建的属性希望被设置为属性，因为我有一些验证函数，我希望在设置属性时运行这些函数。

我有一个代码正在运行，但它产生了一些意想不到的结果。

def func(x):
    """ Example validation function. """
    if x < 0:
        raise ValueError
    return

config = {
    "x": {
        "type": int,
        "default": 0,
        "validate": func
    },
    "y": {
        "type": int,
        "default": 10,
        "validate": func
    },
    "z": {
        "type": str,
        "default": "bar",
        "validate": None
    }
}

def get_property(prop, validate):
    key = f"_{prop}"
    def get_(self):
        return exec(f"self.{key}")
    def set_(self, value):
        if validate is not None:
            validate(value)
        exec(f"self.{key} = value")
    def del_(self):
        exec(f"del self.{key}")
    return property(get_, set_, del_)

def get_Foo(**kwargs):
    class Foo:
        def __init__(self, **_kwargs):
            for k_, v_ in _kwargs.items():
                setattr(self, "_" + k_, None)
                if v_["type"] == str:
                    exec(f"self.{k_} = '{v_['default']}'")
                else:
                    exec(f"self.{k_} = {v_['default']}")
    # Add properties to Foo class
    for k, v in kwargs.items():
        prop_ = get_property(k, v["validate"])
        setattr(Foo, k, prop_)
    # Create Foo class and set defaults
    return Foo(**kwargs)

foo = get_Foo(**config)

现在，当测试时，"setter"似乎在工作，但"getter"不在，"deleter"部分在工作。

print(foo.x)  # prints None
print(foo._x) # prints 0
foo.x = 10
print(foo.x)  # prints None (getter not working)
print(foo._x) # prints 10  (setter works)
foo.x = -1    # raises error (validator in setter works)
del foo.x
print(foo.x)  # AttributeError: 'Foo' object has no attribute '_x' (del sort-of works?)

有人能解释一下结果吗？

Answer 1

感谢juanpa.arrivilaga；切换到getattr、setattr、delatt解决了这个问题。

以下是解决方案：

def get_property(prop, validate):
    key = f"_{prop}"
    def get_(self):
        return getattr(self, key)
    def set_(self, value):
        if validate is not None:
            validate(value)
        setattr(self, key, value)
    def del_(self):
        delattr(self, key)
    return property(get_, set_, del_)

def get_Foo(**kwargs):
    class Foo:
        def __init__(self, **_kwargs):
            for k_, v_ in _kwargs.items():
                setattr(self, "_" + k_, None)
                setattr(self, k_, v_['default'])
    # Add properties to Foo class
    for k, v in kwargs.items():
        prop_ = get_property(k, v["validate"])
        setattr(Foo, k, prop_)
    # Create Foo class and set defaults
    return Foo(**kwargs)

foo = get_Foo(**config)