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

Paul Moore p.f.moore at gmail.com
Sat Oct 3 18:08:13 CEST 2009

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...

Paul.

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