问题描述
谁能告诉我为什么这不起作用?
Can anyone tell me why this isn't working?
>>> import mock >>> @mock.patch('datetime.date.today') ... def today(cls): ... return date(2010, 1, 1) ... >>> from datetime import date >>> date.today() datetime.date(2010, 12, 19)
也许有人可以提出更好的方法?
Perhaps someone could suggest a better way?
推荐答案
有几个问题.
首先,您使用 mock.patch 的方式不太正确.当用作装饰器时,它仅在装饰函数内将给定的函数/类(在本例中为 datetime.date.today)替换为 Mock 对象.所以,只有在你的 today() 中,datetime.date.today 才会是一个不同的函数,这似乎不是你想要的.
First of all, the way you're using mock.patch isn't quite right. When used as a decorator, it replaces the given function/class (in this case, datetime.date.today) with a Mock object only within the decorated function. So, only within your today() will datetime.date.today be a different function, which doesn't appear to be what you want.
你真正想要的似乎更像是这样的:
What you really want seems to be more like this:
@mock.patch('datetime.date.today') def test(): datetime.date.today.return_value = date(2010, 1, 1) print datetime.date.today()
很遗憾,这行不通:
>>> test() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "build/bdist.macosx-10.6-universal/egg/mock.py", line 557, in patched File "build/bdist.macosx-10.6-universal/egg/mock.py", line 620, in __enter__ TypeError: can't set attributes of built-in/extension type 'datetime.date'
这会失败,因为 Python 内置类型是不可变的 - 请参阅 这个答案了解更多详情.
This fails because Python built-in types are immutable - see this answer for more details.
在这种情况下,我将自己继承 datetime.date 并创建正确的函数:
In this case, I would subclass datetime.date myself and create the right function:
import datetime class NewDate(datetime.date): @classmethod def today(cls): return cls(2010, 1, 1) datetime.date = NewDate
现在你可以这样做了:
>>> datetime.date.today() NewDate(2010, 1, 1)