On Sat, 11 Aug 2007 01:57:16 -0700
Talin <[EMAIL PROTECTED]> wrote:
> Taking some ideas from the various threads, here's what I'd like to propose:
>
> (Assume that brackets [] means 'optional field')
>
> [:[type][align][sign][[0]minwidth][.precision]][/fill][!r]
>
> Examples:
>
> :f # Floating point number of natural width
> :f10 # Floating point number, width at least 10
> :f010 # Floating point number, width at least 10, leading zeros
> :f.2 # Floating point number with two decimal digits
> :8 # Minimum width 8, type defaults to natural type
> :d+2 # Integer number, 2 digits, sign always shown
> !r # repr() format
> :10!r # Field width 10, repr() format
> :s10 # String right-aligned within field of minimum width
> # of 10 chars.
> :s10.10 # String right-aligned within field of minimum width
> # of 10 chars, maximum width 10.
> :s<10 # String left-aligned in 10 char (min) field.
> :d^15 # Integer centered in 15 character field
> :>15/. # Right align and pad with '.' chars
> :f<+015.5 # Floating point, left aligned, always show sign,
> # leading zeros, field width 15 (min), 5 decimal places.
>
> Notes:
>
> -- Leading zeros is different than fill character, although the two
> are mutually exclusive. (Leading zeros always go between the sign and
> the number, padding does not.)
> -- For strings, precision is used as maximum field width.
> -- __format__ functions are not allowed to re-interpret '!r'.
>
> I realize that the grouping of things is a little odd - for example, it
> would be nice to put minwidth, padding and alignment in their own little
> group so that they could be processed independently from __format__.
Most custom formatting specs will probably end up putting width,
padding and alignment in their own little group and will delegate
those functions to str.__format__. Like so:
:>30/.,yyyy-MM-dd HH:mm:ss
def __format__(self, specifiers):
align_spec, foo_spec = (specifiers.split(",",1) + [""])[:2]
... format foo ...
return str.__format__(formatted_foo, align_spec.replace("foo", "s"))
(I would suggest allowing ,yyyy-MM-dd as a short form of :,yyyy-MM-dd).
I suspect there will be few cases where it makes sense to intermingle
the width/alignment/padding fields with other fields.
I would move !r to the start of the formatting specification; it should be
prominent when it appears, and format will want to find it easily and
unambiguously rather than leaving it to boilerplate in each __format__
method.
-- Andrew
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