[Python-ideas] Arguments to exceptions
tjreedy at udel.edu
Wed Jul 5 00:54:05 EDT 2017
On 7/5/2017 12:21 AM, Terry Reedy wrote:
> On 7/4/2017 6:31 PM, Greg Ewing wrote:
>> Terry Reedy wrote:
>>> Attaching a *constant* string is very fast, to the consternation of
>>> people who would like the index reported.
> Actually, the constant string should be attached to the class, so there
> is no time needed.
I should say, a default string, or parameter default value. I just
checked and Python gives the numerator type the ZeroDivisionError
message and the sequence type in the IndexError message, so scratch that
>> Seems to me that storing the index as an attribute would help
>> with this. It shouldn't be much slower than storing a constant
> Given that the offending int is available as a Python int, then storing
> a reference should be quick, though slower than 0 (see above ;-).
0 is wrong. Just a reference storage in both cases.
>> and formatting the message would be deferred until
>> it's needed, if at all.
> I agree that this would be the way to do it. I will let an advocate of
> this enhancement lookup the rejected issue (there may be more than one)
> proposing to make the bad index available and see if this is the actual
> proposal rejected and if so, why (better than I may remember).
> It occurs to me that if the exception object has no reference to any
> python object, then all would be identical and only one cached instance
> should be needed. I checked and neither IndexError nor
> ZeroDivisionError do this.
Terry Jan Reedy
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