在 Python 中捕获 KeyError [英] Catch KeyError in Python

问题描述

如果我运行代码:

connection = manager.connect("I2Cx")

程序崩溃并报告 KeyError 因为 I2Cx 不存在(应该是 I2C).

The program crashes and reports a KeyError because I2Cx doesn't exist (it should be I2C).

但如果我这样做:

try:
    connection = manager.connect("I2Cx")
except Exception, e:
    print e

它不会为 e 打印任何内容.我希望能够打印抛出的异常.如果我用除以零操作尝试同样的事情，它会在两种情况下被捕获并正确报告.我在这里错过了什么?

It doesn't print anything for e. I would like to be able to print the exception that was thrown. If I try the same thing with a divide by zero operation it is caught and reported properly in both cases. What am I missing here?

推荐答案

如果它引发了一个没有消息的 KeyError，那么它不会打印任何东西.如果你这样做...

If it's raising a KeyError with no message, then it won't print anything. If you do...

try:
    connection = manager.connect("I2Cx")
except Exception as e:
    print repr(e)

...你至少会得到异常类名.

...you'll at least get the exception class name.

更好的选择是使用多个 except 块，并且只捕获"您打算处理的异常...

A better alternative is to use multiple except blocks, and only 'catch' the exceptions you intend to handle...

try:
    connection = manager.connect("I2Cx")
except KeyError as e:
    print 'I got a KeyError - reason "%s"' % str(e)
except IndexError as e:
    print 'I got an IndexError - reason "%s"' % str(e)

有正当理由可以捕获所有异常，但如果这样做，您几乎总是应该重新引发它们...

There are valid reasons to catch all exceptions, but you should almost always re-raise them if you do...

try:
    connection = manager.connect("I2Cx")
except KeyError as e:
    print 'I got a KeyError - reason "%s"' % str(e)
except:
    print 'I got another exception, but I should re-raise'
    raise

...因为你可能不想在用户按下 CTRL-C 时处理 KeyboardInterrupt，也不想在 try 时处理 SystemExit-block 调用 sys.exit().

...because you probably don't want to handle KeyboardInterrupt if the user presses CTRL-C, nor SystemExit if the try-block calls sys.exit().

这篇关于在 Python 中捕获 KeyError的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！