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

Antoine Pitrou solipsis at pitrou.net
Sat Oct 3 18:00:48 CEST 2009

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

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.



More information about the Python-Dev mailing list