[Python-Dev] PEP 460 reboot

Guido van Rossum guido at python.org
Mon Jan 13 22:51:12 CET 2014

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.

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

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.

--Guido van Rossum (python.org/~guido)

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