Question

我在python中扩展date类时遇到了问题。

然而，由于日期是静态类，我还没有按照它应该的那样工作。我尝试修改datetime上的代码库，因为此类从date扩展。但是，失败了。

问题是：

如何修改代码使其工作如下：

ed = ExtendDate（2011,1,1，week = 3，quarter = 3）

print ed.week＃3

如何处理python静态类中的__new__和__init__（理论上）？
如何扩展日期类（一般情况下）？

感谢。

class ExtendDate(date):
    """Extend to have week and quarter property"""

    #
    # def __init__(self, year, month, day, week=None, quarter=None):
    #     pass

    def __init__(self, year, month, day, week=None, quarter=None):
        print 0
        super(ExtendDate, self).__init__(year,month,day)
        print 1
        self._week = week
        self._quarter = quarter


    @staticmethod
    def __new__(cls, year, month, day, week=None, quarter=None):
        cls._week = 1
        super(ExtendDate, cls).__new__(year, month, day)

    def __cmp__(self, other):
        if self.cmp_year(other) in [-1,0,1]:
            return self.cmp_year(other)

        if hasattr(self, 'quarter'):
            return self.cmp_quarter(other)

        if hasattr(self, 'week'):
            return self.cmp_week(other)
        # TODO: test - what if it's just a normal date object ?
        pass

    def cmp_quarter(self, other):
        if self.quarter < other.quarter:
            return -1
        elif self.quarter == other.quarter:
            return 0
        elif self.quarter > other.quarter:
            return 1

    def cmp_week(self, other):
        if self.week < other.week:
            return -1
        elif self.week == other.week:
            return 0
        elif self.week > other.week:
            return 1

    def cmp_year(self, other):
        if self.year < other.year:
            return -1
        elif self.year == other.year:
            return 0
        elif self.year > other.year:
            return 1

    def __repr__(self):
        return 'year:' + str(self.year) + ' ' + \
              'quarter:' + str(self.quarter) + ' ' + \
              'month:' + str(self.month) + ' '+ \
              'week:' + str(self.week) + ' '+ \
              'day:' + str(self.day) + ' '

    week = property(lambda self: 0)
    quarter = property(lambda self: 0)

    @week.setter
    def week(self, value):
        self._week = value

    @quarter.setter
    def quarter(self, value):
        self._quarter = value

Answer 1

__new__不应该使用@staticmethod进行修饰（隐式地使用类方法，不应使用装饰器）。并且它应该返回创建的实例，代码正在修改cls（它不应该）并且不返回super __new__调用的结果（它应该）。另外，如果您提供__new__（使该课程在逻辑上不可变），则您不应提供__init__。

真的，你想要的代码就像：

class ExtendDate(date):
    """Extend to have week and quarter property"""
    __slots__ = '_week', '_quarter'  # Follow date's lead and limit additional attributes

    def __new__(cls, year, month, day, week=None, quarter=None):
        self = super(ExtendDate, cls).__new__(cls, year, month, day)
        self._week = week
        self._quarter = quarter
        return self

据推测，您还需要功能性吸气剂，例如

    @property
    def week(self):
        return self._week

    # ... etc. ...

Answer 2

当@ShadowRanger回答时，我更改了一些行以使其正常工作。

主要变化是__new__(cls, year, month, day)：

from datetime import date


class ExtendDate(date):
    """Extend to have week and quarter property"""
    __slots__ = '_week', '_quarter'


    def __new__(cls, year, month, day, week=None, quarter=None):
        # self = super(ExtendDate, cls).__new__(year, month, day)
        self = date.__new__(cls, year, month, day)
        self._week = week
        self._quarter = quarter
        return self

    def __cmp__(self, other):
        if self.cmp_year(other) in [-1,0,1]:
            return self.cmp_year(other)

        if hasattr(self, 'quarter'):
            return self.cmp_quarter(other)

        if hasattr(self, 'week'):
            return self.cmp_week(other)
        # TODO: test - what if it's just a normal date object ?
        pass

    def cmp_quarter(self, other):
        if self.quarter < other.quarter:
            return -1
        elif self.quarter == other.quarter:
            return 0
        elif self.quarter > other.quarter:
            return 1

    def cmp_week(self, other):
        if self.week < other.week:
            return -1
        elif self.week == other.week:
            return 0
        elif self.week > other.week:
            return 1

    def cmp_year(self, other):
        if self.year < other.year:
            return -1
        elif self.year == other.year:
            return 0
        elif self.year > other.year:
            return 1

    def __repr__(self):
        return 'year:' + str(self.year) + ' ' + \
              'quarter:' + str(self.quarter) + ' ' + \
              'month:' + str(self.month) + ' '+ \
              'week:' + str(self.week) + ' '+ \
              'day:' + str(self.day) + ' '


    @property
    def week(self):
        return self._week

    @property
    def quarter(self):
        return self._quarter


ed = ExtendDate(2011,1,2,3,4)
print type(ed)
print ed._week

延长日期等级

2 个答案: