如何在 Python 中捕获自定义异常 [英] How to catch custom exception in Python

问题描述

我正在使用一个 python 库，其中有一次异常定义如下:

I'm using a python library in which at one point an exception is defined as follows:

raise Exception("Key empty")

我现在希望能够捕获该特定异常，但我不知道该怎么做.

I now want to be able to catch that specific exception, but I'm not sure how to do that.

我尝试了以下

try:
    raise Exception('Key empty')
except Exception('Key empty'):
    print 'caught the specific exception'
except Exception:
    print 'caught the general exception'

但这只是打印出caught the general exception.

有人知道我如何捕获特定的 Key empty 异常吗?欢迎所有提示！

Does anybody know how I can catch that specific Key empty exception? All tips are welcome!

推荐答案

定义您的例外:

class KeyEmptyException(Exception):
    def __init__(self, message='Key Empty'):
        # Call the base class constructor with the parameters it needs
        super(KeyEmptyException, self).__init__(message)

使用它:

try:
    raise KeyEmptyException()
except KeyEmptyException as e:
    print e

更新:基于 OP 发布的评论中的讨论:

Update: based on the discussion in comment OP posted:

但是这个库不在我的控制之下.它是开源的，所以我可以编辑它，但我最好尝试在不编辑库的情况下捕获它.这不可能吗?

But the lib is not under my control. It's open source, so I can edit it, but I would preferably try to catch it without editing the library. Is that not possible?

说库引发异常

# this try is just for demonstration 
try:

    try:
        # call your library code that can raise `Key empty` Exception
        raise Exception('Key empty')
    except Exception as e:
        # if exception occurs, we will check if its 
        # `Key empty` and raise our own exception
        if str(e) == 'Key empty':
            raise KeyEmptyException()
        else:
            # else raise the same exception
            raise e
except Exception as e:
    # we will finally check what exception we are getting
    print('Caught Exception', e)

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