如何强制确保类属性是特定类型？

如何强制/确保类属性是特定类型？

您可以像其他答案一样使用属性-因此，如果您想约束单个属性，例如说“ bar”，并将其约束为整数，则可以编写如下代码：

class Foo(object):    def _get_bar(self):        return self.__bar    def _set_bar(self, value):        if not isinstance(value, int): raise TypeError("bar must be set to an integer")        self.__bar = value    bar = property(_get_bar, _set_bar)

这有效：

>>> f = Foo()>>> f.bar = 3>>> f.bar3>>> f.bar = "three"Traceback (most recent call last):  File "<stdin>", line 1, in <module>  File "<stdin>", line 6, in _set_barTypeError: bar must be set to an integer>>>

（还有一种新的属性编写方法，使用内置的“属性”作为getter方法的装饰器-但我更喜欢旧方法，就像我上面提到的那样）。

当然，如果您的类具有很多属性，并希望以这种方式保护所有属性，那么它就会变得冗长。不用担心-
Python的自省功能允许创建一个类装饰器，该装饰器可以用最少的行自动实现。

def getter_setter_gen(name, type_):    def getter(self):        return getattr(self, "__" + name)    def setter(self, value):        if not isinstance(value, type_): raise TypeError(f"{name} attribute must be set to an instance of {type_}")        setattr(self, "__" + name, value)    return property(getter, setter)def auto_attr_check(cls):    new_dct = {}    for key, value in cls.__dict__.items():        if isinstance(value, type): value = getter_setter_gen(key, value)        new_dct[key] = value    # Creates a new class, using the modified dictionary as the class dict:    return type(cls)(cls.__name__, cls.__bases__, new_dct)

然后，您仅用

auto_attr_check

作类装饰器，并在类主体中声明要与属性也需要约束的类型相等的属性：

...     ... @auto_attr_check... class Foo(object):...     bar = int...     baz = str...     bam = float... >>> f = Foo()>>> f.bar = 5; f.baz = "hello"; f.bam = 5.0>>> f.bar = "hello"Traceback (most recent call last):  File "<stdin>", line 1, in <module>  File "<stdin>", line 6, in setterTypeError: bar attribute must be set to an instance of <type 'int'>>>> f.baz = 5Traceback (most recent call last):  File "<stdin>", line 1, in <module>  File "<stdin>", line 6, in setterTypeError: baz attribute must be set to an instance of <type 'str'>>>> f.bam = 3 + 2jTraceback (most recent call last):  File "<stdin>", line 1, in <module>  File "<stdin>", line 6, in setterTypeError: bam attribute must be set to an instance of <type 'float'>>>>