用类的内置方法实现类型检查

1.利用重写__setattr__来实现。

import logging

logger = logging.getLogger('logger')
streamhandler = logging.StreamHandler()
logger.setLevel(logging.DEBUG)
streamhandler.setLevel(logging.DEBUG)
streamhandler.setFormatter(logging.Formatter(
    '%(asctime)s - %(name)s - %(levelname)s - %(message)s'))
logger.addHandler(streamhandler)


def typeassist(**kwargs):
    def new_cls(cls):
        def redefine(self, key, value):
            if not isinstance(value, kwargs[key]):
                logger.log(level=logging.ERROR, msg='TypeError')
                self.__dict__[key] = None
            else:
                self.__dict__[key] = value
        setattr(cls, '__setattr__', redefine)
        return cls
    return new_cls


@typeassist(name=str, age=int, result=float)
class Student:
    def __init__(self, name, age, result):
        self.name = name
        self.age = age
        self.result = result

    def __str__(self):
        return str(self.__dict__)


m = Student('sasd', 56, 45.0)
p = Student('SSS', 12, 4)
print(p)
print(m)

2.利用描述符来实现。

import logging

logger = logging.getLogger('logger')
streamhandler = logging.StreamHandler()
logger.setLevel(logging.DEBUG)
streamhandler.setLevel(logging.DEBUG)
streamhandler.setFormatter(logging.Formatter(
    '%(asctime)s - %(name)s - %(levelname)s - %(message)s'))
logger.addHandler(streamhandler)


class Descriptor:
    def __init__(self, attrname, attrtype):
        self.attrname = attrname
        self.attrtype = attrtype

    def __set__(self, instance, value):
        if not isinstance(value, self.attrtype):
            logger.log(level=logging.ERROR, msg='TypeError')
            self.__dict__[instance] = None
            instance.__dict__[self.attrname] = None  # 注意，此处是为了维护属性字典的统一性
        else:
            self.__dict__[instance] = value
            instance.__dict__[self.attrname] = value  # 同上

    def __get__(self, instance, owner):
        return self.__dict__[instance]


def typeassist(**kwargs):
    def new_cls(cls):
        for attrname, attrtype in kwargs.items():
            setattr(cls, attrname, Descriptor(attrname, attrtype))
        return cls
    return new_cls


@typeassist(name=str, age=int, result=float)
class Student:
    def __init__(self, name, age, result):
        self.name = name
        self.age = age
        self.result = result

    def __str__(self):
        return str(self.__dict__)


m = Student('sasd', 56, 45.0)
p = Student('SSS', 12, 4)
print(p)
print(m)