使用相同的函数设置多个类属性

Question

我想创建一个python类，其中几个属性的类型为datetime.date，但也可以使用str或datetime.datetime实例设置它们。到目前为止我有这个：

import datetime


def my_date_fn(date_in):
    """
    Return a datetime.date object from either a string (e.g. "2018/01/04"),
    datetime.datetime or datetime.date object.
    """
    if type(date_in) is str:
        return datetime.date(*map(int, date_in.split('/')))
    elif type(date_in) is datetime.datetime:
        return date_in.date()
    elif type(date_in) is datetime.date:
        return date_in


class MyClass(object):
    """
    Class to contain date information.
    """
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    @property
    def a(self):
        return self._a

    @a.setter
    def a(self, value):
        self._a = my_date_fn(value)

    @property
    def b(self):
        return self._b

    @b.setter
    def b(self, value):
        self._b = my_date_fn(value)

    @property
    def c(self):
        return self._c

    @c.setter
    def c(self, value):
        self._c = my_date_fn(value)


test = MyClass('2017/7/7', datetime.date(2012, 8, 4),
               datetime.datetime(2001, 5, 3, 12, 0))

for x in ['a', 'b', 'c']:
    print getattr(test, x), type(getattr(test, x))

这工作正常，但有很多重复的代码与@property和@*.setter函数。有没有更优雅的方式来做到这一点？

Answer 1

简单地说，定义一个函数：

def date_property(name):
    def set_date(self, date_in):
        """
        Return a datetime.date object from either a string (e.g. "2018/01/04"),
        datetime.datetime or datetime.date object.
        """
        if isinstance(date_in, str):
            date_in = datetime.date(*map(int, date_in.split('/')))
        elif isinstance(date_in, datetime.datetime):
            date_in = date_in.date()
        elif isinstance(date_in, datetime.date):
            pass
        else:
            raise TypeError()
        setattr(self, name, date_in)
    return property(lambda self: getattr(self, name), set_date)


class MyClass(object):
    """
    Class to contain date information.
    """
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    a = date_property('_a')
    b = date_property('_b')
    c = date_property('_c')