Question

在某些情况下，我需要引发异常，因为内置异常不适用于我的程序。定义异常后，python会同时引发我的异常和内置异常，如何处理这种情况？我只想打印我的吗？

class MyExceptions(ValueError):
    """Custom exception."""
    pass

try:
    int(age)
except ValueError:
    raise MyExceptions('age should be an integer, not str.')

输出：

Traceback (most recent call last):
  File "new.py", line 10, in <module>
    int(age)
ValueError: invalid literal for int() with base 10: 'merry_christmas'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "new.py", line 12, in <module>
    raise MyExceptions('age should be an integer, not str.')
__main__.MyExceptions: age should be an integer, not str.

我想打印这样的东西：

Traceback (most recent call last):
  File "new.py", line 10, in <module>
    int(age)
MyException: invalid literal for int() with base 10: 'merry_christmas'

Answer 1

在引发自定义异常时添加from None：

raise MyExceptions('age should be an integer, not str.') from None

有关更多信息，请参见PEP 409 -- Suppressing exception context。

Answer 2

尝试将from lxml import html raw_source = """<html> <a href="HarryPotter:Chamber of Secrets"> text </a> <a href="HarryPotter:Prisoners in Azkabahn"> text </a> </html>""" source = html.fromstring(raw_source) for link in source.xpath('//a'): print(link.xpath('substring-after(@href, "HarryPotter:")'))更改为raise MyExceptions('age should be an integer, not str.')

Answer 3

您可以禁止异常上下文，并将消息从ValueError传递到您的自定义异常：

try:
    int(age)
except ValueError as e:
    raise MyException(str(e)) from None
    # raise MyException(e) from None  # works as well

如何提出我的例外而不是内置例外？

3 个答案: