[Python-3000] More PEP 3101 changes incoming

Tue Aug 14 09:55:35 CEST 2007

Ron Adam wrote:
>> Greg Ewing wrote:
>> Ron Adam wrote:
>>>>> The digits value are number of digits before the decimal. This doesn't 
>>> include the other symbols used in the field so it isn't the same as a field 
>>> width.
>> How does this work with formats where the number of
>> digits before the decimal can vary, but before+after
>> is constant?
>> I think this is what you're looking for.
>> f>15,.3 #15 field width, 3 decimal places, right aligned.
>> In this case the sign will be right before the most significant digit.
>> Or you could use...
>> f 10.3 # total width = 15
>> In this one, the sign would be to the far left of the field. So they are 
> not the same thing. The space is used here to make positives numbers the 
> same width as negatives values.
>>>> Also, my feeling about the whole of this is that
>> it's too complicated. It seems like you can have
>> at least three numbers in a format, and at first
>> glance it's quite confusing as to what they all
>> mean.
>> Well, at first glance so is everything else that's been suggested, it's 
> because we are doing a lot in a very little space. In this case we are 
> adding just a touch of complexity to the syntax in order to use grouping to 
> remove complexity in understanding the expression.
>> These are all field width terms:
>> >10 right align in field 10
> ^15/_ center in field 15, pad with underscores
> 20/* left align in field 20, pad with *
>> They are easy to identify because other terms do not contain '<^>/'. And 
> sense they are separate from other format terms, once you get it, you've 
> got it. Nothing more to remember here.
>> It doesn't make sense to put signs in front of field widths because the 
> signs have no relation to the field width at all.
>>> These are all number formats:
>> +10.4
> (10.4)
> .6
> ' 9.3' Quoted so you can see the space.
> 10.
>> Here, we don't use alignment symbols. Alignments have no meaning in the 
> context of number of digits. So these taken as a smaller chunk of the 
> whole will also be easier to remember. There are no complex interactions 
> between field alignment terms, and number terms this way. That makes 
> simpler to understand and learn.
>>> Lets take apart the alternative syntax.
>> f<+15.2
>> f fixed point # of decimals is specified
>> < align left (field attribute)
>> + sign (number attribute)
>> 15 width (field attribute)
>> .2 decimals (number attribute)

Then why not have something more readable like
 al;s+;w15;d2
This is longer that <+15.2, but IMHO much more readable, because it's 
clear where each specifier ends and begins.
Servus,
 Walter