Home Original page

[Python-Dev] summary of transitioning from % to {} formatting

R. David Murray rdmurray at bitdance.com
Sat Oct 3 18:19:32 CEST 2009 
On Sat, 3 Oct 2009 at 17:08, Paul Moore wrote:
> 2009/10/3 Antoine Pitrou <solipsis at pitrou.net>:
>> Steven Bethard <steven.bethard <at> gmail.com> writes:
>>>
>>>   If %-formatting is to be deprecated, the transition strategy here
>>>   is trivial. However, no one has yet written translators, and it is
>>>   not clear what heuristics should be used, e.g. should the method
>>>   just try %-formatting first and then {}-formatting if it fails?
>>
>> This would be a reasonable heuristic. It should be done only on the first call,
>> though, and then the result remembered (for both performance reasons and
>> consistency).
>>
>> The cases where a format string would function in both formatting styles and
>> expect the same parameters must be very rare in the real world.
>
> Define "fails":
>
>>>> "{a} {b} c" % {'a':12}
> '{a} {b} c'
>
> That didn't fail...

Also, what if both fail?  Which failure's error message gets printed?

--David (RDM)
More information about the Python-Dev mailing list