子类化datetime.datetime [英] Subclassing datetime.datetime
问题描述
我正在考虑创建一个python datetime子类,该类在创建时会提供默认时区。
I'm looking into creating a python datetime-subclass which provides a default timezone when created.
为了使这个问题简单,让我们假设我总是想要将我的日期时间硬编码为UTC。
For the sake of keeping this question simple, let's assume I always want to hard-code my datetimes to be in UTC.
我不知道以下原因为何:
I can't figure out why the following works:
import datetime, dateutil.tz
def foo(*args, **kwargs):
kwargs['tzinfo'] = dateutil.tz.tzutc()
return datetime.datetime(*args, **kwargs)
但以下操作无效:
class Foo(datetime.datetime):
def __init__(self, *args, **kwargs):
kwargs['tzinfo'] = dateutil.tz.tzutc()
super(Foo, self).__init__(*args, **kwargs)
运行第一种方法给我期望的datetime对象:
Running the first method gives me the datetime object I expect:
>>> foo(2012, 11, 10)
datetime.datetime(2012, 11, 10, 0, 0, tzinfo=tzutc())
>>> foo(2012, 11, 10).tzinfo is None
False
但是创建实例
>>> Foo(2012, 11, 10)
Foo(2012, 11, 10, 0, 0)
>>> Foo(2012, 11, 10).tzinfo is None
True
关于什么的任何想法
谢谢!
推荐答案
提供解决方案,如为什么不能为子类datetime.date 所述。完整,这要感谢 dano 的链接。
Providing the solution, as explained in Why can't I subclass datetime.date? for the sake of completeness, thanks to dano for the link.
由于datetime对象是不可变的,因此必须在新功能中实现额外的功能:
The extra functionality has to be implemented in new since the datetime object is immutable:
class Foo(datetime.datetime):
def __new__(cls, *args, **kwargs):
kwargs['tzinfo'] = dateutil.tz.tzutc()
return datetime.datetime.__new__(cls, *args, **kwargs)
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