我在我的代码中有这个try块:
try:
do_something_that_might_raise_an_exception()
except ValueError as err:
errmsg = 'My custom error message.'
raise ValueError(errmsg)
严格地说，我实际上引发了另一个ValueError，而不是do_something…()抛出的ValueError，在这种情况下被称为err。如何将自定义消息附加到错误?我尝试以下代码，但失败，由于错误，ValueError实例，不可调用:
try:
do_something_that_might_raise_an_exception()
except ValueError as err:
errmsg = 'My custom error message.'
raise err(errmsg)
当前回答
当前的答案对我来说并不是很好，如果没有重新捕获异常，则不会显示附加的消息。
但是像下面这样做既保持跟踪，又显示附加的消息，不管是否重新捕获异常。
try:
raise ValueError("Original message")
except ValueError as err:
t, v, tb = sys.exc_info()
raise t, ValueError(err.message + " Appended Info"), tb
(我使用Python 2.7，在Python 3中没有尝试过)
其他回答
这是我在Python 2.7和3中用来修改异常消息的函数。X，同时保留原始的回溯。需要6个
def reraise_modify(caught_exc, append_msg, prepend=False):
"""Append message to exception while preserving attributes.
Preserves exception class, and exception traceback.
Note:
This function needs to be called inside an except because
`sys.exc_info()` requires the exception context.
Args:
caught_exc(Exception): The caught exception object
append_msg(str): The message to append to the caught exception
prepend(bool): If True prepend the message to args instead of appending
Returns:
None
Side Effects:
Re-raises the exception with the preserved data / trace but
modified message
"""
ExceptClass = type(caught_exc)
# Keep old traceback
traceback = sys.exc_info()[2]
if not caught_exc.args:
# If no args, create our own tuple
arg_list = [append_msg]
else:
# Take the last arg
# If it is a string
# append your message.
# Otherwise append it to the
# arg list(Not as pretty)
arg_list = list(caught_exc.args[:-1])
last_arg = caught_exc.args[-1]
if isinstance(last_arg, str):
if prepend:
arg_list.append(append_msg + last_arg)
else:
arg_list.append(last_arg + append_msg)
else:
arg_list += [last_arg, append_msg]
caught_exc.args = tuple(arg_list)
six.reraise(ExceptClass,
caught_exc,
traceback)
这个代码模板应该允许您用自定义消息引发异常。
try:
raise ValueError
except ValueError as err:
raise type(err)("my message")
使用的错误消息引发新的异常
raise Exception('your error message')
or
raise ValueError('your error message')
在你想要引发它或使用'from'将错误消息附加(替换)到当前异常的地方(Python 3。只支持X):
except ValueError as e:
raise ValueError('your message') from e
try:
try:
int('a')
except ValueError as e:
raise ValueError('There is a problem: {0}'.format(e))
except ValueError as err:
print err
打印:
There is a problem: invalid literal for int() with base 10: 'a'
如果你想自定义错误类型，你可以做的一件简单的事情就是基于ValueError定义一个错误类。
