你的问题与空闲无关。您看到的行为都来自Python。从命令行以交互方式运行当前存储库CPython,我们可以看到您报告的行为。

Python 3.7.0a2+ (heads/pr_3947:01eae2f721, Oct 22 2017, 14:06:43)
[MSC v.1900 32 bit (Intel)] on win32

>>> raise KeyError('This is a \n Line break')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'This is a \n Line break'
>>> s = 'This is a \n Line break'

>>> s
'This is a \n Line break'
>>> print(s)
This is a
 Line break
>>> raise Exception('This is a \n Line break')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
Exception: This is a
 Line break
>>> raise IndexError(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: This is a
 Line break
>>> try:
...   raise  KeyError('This is a \n Line break')
... except KeyError as e:
...   print(e)

'This is a \n Line break'
>>> try:
...   raise  KeyError('This is a \n Line break')
... except KeyError as e:
...   print(e.args[0])

This is a
 Line break

我不知道为什么KeyError的行为与索引器不同,但打印e.args[0]应该适用于所有异常。

编辑

this old tracker issue ,其中引用了 KeyError 源代码:

/* If args is a tuple of exactly one item, apply repr to args[0].
       This is done so that e.g. the exception raised by {}[''] prints
         KeyError: ''
       rather than the confusing
         KeyError
       alone.  The downside is that if KeyError is raised with an
explanatory
       string, that string will be displayed in quotes.  Too bad.
       If args is anything else, use the default BaseException__str__().
    */

此部分出现在 KeyError_str 中的对象定义 Objects/exceptions.c 的Python源代码。

我将提到你的问题,作为这种差异的另一种表现。

那里 获得所需行为的一种方法:只需子类 str 和覆盖 __repr__

    class KeyErrorMessage(str):
        def __repr__(self): return str(self)
    msg = KeyErrorMessage('Newline\nin\nkey\nerror')
    raise KeyError(msg)

打印:

回溯(最近一次呼叫最后一次):
...
文件“”,第5行,in
raise KeyError(消息)
关键错误:换行
在里面

错误