[issue18163] Add a 'key' attribute to KeyError

[Mark Dickinson]

Mark Dickinson added the comment:

+1.  I recently chastised a colleague for doing "raise KeyError(long_message)" instead of "raise KeyError(missing_item)".  When I went to the standard library to support my POV, I found (to my chagrin) a big mix of the two styles.


>>> from collections import ChainMap
>>> d = ChainMap({}, {})
>>> try:
...     d.pop('not there')
... except KeyError as e:
...     key, = e.args
... 
>>> key
"Key not found in the first mapping: 'not there'"

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nosy: +mark.dickinson

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<http://bugs.python.org/issue18163>
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