[Python-Dev] summary of transitioning from % to {} formatting (original) (raw)

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 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)

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