[Python-Dev] cpython (3.2): Issue #14123: Explicitly mention that old style % string formatting has caveats (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Sun Feb 26 19:54:00 CET 2012

On Sun, 26 Feb 2012 19:50:10 +0100 martin at v.loewis.de wrote:

>> - The formatting operations described here are obsolete and may go away >> in future >> - versions of Python. Use the new :ref:string-formatting in new code. >> + The formatting operations described here are modelled on C's printf() >> + syntax. They only support formatting of certain builtin types. The >> + use of a binary operator means that care may be needed in order to >> + format tuples and dictionaries correctly. As the new >> + :ref:string-formatting syntax is more flexible and handles tuples and >> + dictionaries naturally, it is recommended for new code. However, there >> + are no current plans to deprecate printf-style formatting. >> > > Please consider just deleting the last sentence. Documentation is meant for > users (often new users) and not core devs. As such, I just don't see what > it adds. If the aim to to document this intent somewhere, a PEP would be a > better place than the formal documentation.

I'd rather leave the last sentence, and delete the penultimate sentence. The last sentence is useful information to the end user ("we will not deprecate printf-style formatting, so there is no need to change existing code"). I'd drop the penultimate sentence because there is no consensus that it is a useful recommendation (and it is certainly not a statement of fact).

It would be nice to call it something else than "printf-style formatting". While it is certainly modelled on printf(), knowledge of C or printf is not required to understand %-style formatting, nor even to appreciate it.

Regards

Antoine.

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