Message85983
Prompted by
http://mail.python.org/pipermail/python-ideas/2009-April/004048.html
The current error message issued when trying to use the get item ([])
operator on an object that does not define __getitem__ can be hard to
understand:
>>> class A(object): pass
...
>>> A()['a']
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'A' object is unsubscriptable
Problems observed:
- "unsubscriptable" is easily misread in haste as "unscriptable", which
can be quite confusing, especially to newbies
- "subscripting" is not frequently used to describe the [] operator,
making the message more difficult to decipher (again, esp. for newbies)
- the underlying lack of a __getitem__ method is not mentioned, thus not
making it obvious how to remedy the error
Suggestion:
Use exception chaining and rephrase the error message to get something like:
AttributeError: class 'A' has no attribute '__getitem__'
The above exception was the direct cause of the following exception:
TypeError: 'A' object does not support the 'get item' operator
Similar changes should be made to __setitem__ & __delitem__. |
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Date |
User |
Action |
Args |
2009-04-15 06:32:12 | cvrebert | set | recipients:
+ cvrebert |
2009-04-15 06:32:11 | cvrebert | set | messageid: <1239777131.98.0.31222273519.issue5760@psf.upfronthosting.co.za> |
2009-04-15 06:32:10 | cvrebert | link | issue5760 messages |
2009-04-15 06:32:09 | cvrebert | create | |
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