iter()无法与datetime.now()一起使用 [英] iter() not working with datetime.now()
问题描述
Python 3.6.1中的一个简单代码段:
A simple snippet in Python 3.6.1:
import datetime
j = iter(datetime.datetime.now, None)
next(j)
返回:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
StopIteration
而不是打印出经典的 now()
与每个 next()
的行为。
instead of printing out the classic now()
behavior with each next()
.
我已经看到类似的代码在Python中工作3.3,我在3.6.1版本中是否缺少某些东西或有什么更改?
I've seen similar code working in Python 3.3, am I missing something or has something changed in version 3.6.1?
推荐答案
这肯定是Python 3.6中引入的错误.0b1。 iter()
实现最近切换为使用 _PyObject_FastCall()
(优化,请参见问题27128 ),并且必须是此调用才能打破此问题。
This is definitely a bug introduced in Python 3.6.0b1. The iter()
implementation recently switched to using _PyObject_FastCall()
(an optimisation, see issue 27128), and it must be this call that is breaking this.
由Argument Clinic解析支持的其他C classmethod
方法遇到相同的问题:
The same issue arrises with other C classmethod
methods backed by Argument Clinic parsing:
>>> from asyncio import Task
>>> Task.all_tasks()
set()
>>> next(iter(Task.all_tasks, None))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
StopIteration
如果需要解决方法,则将可调用项包装在<$ c中$ c> functools.partial()对象:
If you need a work-around, wrap the callable in a functools.partial()
object:
from functools import partial
j = iter(partial(datetime.datetime.now), None)
我提交了问题30524- iter(classmethod,sentinel)对于Argument Clinic类方法无效吗? 与Python项目。此修补程序已着陆,并且是3.6.2rc1的一部分。
I filed issue 30524 -- iter(classmethod, sentinel) broken for Argument Clinic class methods? with the Python project. The fix for this has landed and is part of 3.6.2rc1.
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