python – 子类化datetime：在算术运算之后是否有更好的方法来维

我最近遇到了一个情境,我需要将datetime.datetime和datetime.timedelta子类化,以便添加一些方法.但是,我立刻发现,当我希望它返回mydatetime.mydatetime实例时,任何算术运算都会返回datetime.datetime对象.以下是同事帮助我解决这个问题的解决方案.有没有人有更简洁或方便的建议？我在这里做了什么有危险吗？我错过了什么重要的事吗？

from datetime import datetime,timedelta

def _to_mydatetime(native):
    '''Instantiates object of appropriate class based on class
    of the input object.'''
    if hasattr(native,'timetuple'):
        return mydatetime(*native.timetuple()[:6])
    else:
        return mytimedelta(native.days,native.seconds)

class mydatetime(datetime):
    '''Subclass of datetime'''
    def __add__(self,other):
        result = super(mydatetime,self).__add__(other)
        return _to_mydatetime(result)

    def __sub__(self,self).__sub__(other)
        return _to_mydatetime(result)

class mytimedelta(timedelta):
    def __add__(self,other):
        result = super(mytimedelta,self).__sub__(other)
        return _to_mydatetime(result)

    def __div__(self,self).__div__(other)
        return _to_mydatetime(result)

    def __rmul__(self,self).__rmul__(other)
        return _to_mydatetime(result)

    def __mul__(self,self).__mul__(other)
        return _to_mydatetime(result)

from datetime import *

def convproxy(methods,converter):
    def f(cls):
        def _proxyfactory(method):
            def _convproxy(self,*args,**kwargs):
                return converter(getattr(super(cls,self),method)(*args,**kwargs))
            return _convproxy
        for m in methods:
            setattr(cls,m,_proxyfactory(m))
        return cls
    return f

@convproxy(('__add__','__sub__'),lambda d:mydatetime(d.timetuple()[:6]))
class mydatetime(datetime):
    pass

@convproxy(('__add__','__sub__','__div__','__rmul__','__mul__'),
        lambda t:mytimetuple(t.days,t.seconds))
class mytimedelta(timedelta):
    pass