[Python-Dev] PEP 460 reboot (original) (raw)

MRAB python at mrabarnett.plus.com
Tue Jan 14 02:03:44 CET 2014

On 2014-01-13 21:51, Guido van Rossum wrote:

Terminology. Let's use the official terminology rather than making stuff up.

The docs at http://docs.python.org/3/library/string.html#formatspec use the following terminology: Replacement field: {...}; contains field name, conversion, format spec in that order, all optional. Field name: either a decimal integer (referring to an argument by position) or an identifier (by name), or omitted (uses the next available position). Conversion: !r, !s, !a; these refer to repr(), str(), ascii() to the value, and then the format spec applies to the resulting string. If all you wanted to do was interpolate bytes then you could define a new conversion !b. This would, however, mean that the format spec would be applied to bytes.

Format spec: colon, bunch of stuff, type; the type is a letter such as d (decimal) or s (string), and the stuff between the colon and the type is used to specify field width, alignment, sign, padding and such.

Also. {:b} means binary (i.e. numbers in base 2). I'm not sure what this leaves for interpolating bytes if we don't want to use {:s}. The docs at http://docs.python.org/3/library/stdtypes.html#printf-style-string-formatting don't show %b so it could still be used there, but it would be nicer to be consistent.

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