[Python-3000] Need Decimal.__format__

[Nicko van Someren]

On 31 Aug 2007, at 02:36, Talin wrote:
...
> Also, I'm interested in suggestions as to any other standard types  
> that
> ought to have a __format__ method, other than the obvious Date/Time
> classes. What kinds of things do people usually want to print?

For years I've thought that various collection types would benefit  
from better formatters.  If space is limited (e.g. fixed width  
fields) then lists, tuples and sets are often better displayed  
truncated, with an ellipsis in lieu of the remainder of the  
contents.  Being able to have a standard way to print your list as  
[2, 3, 5, 7, 11,...] when you only have 20 characters would  
frequently be useful.  Having a formatter directive for collections  
to ask for the contents without the enclosing []/()/{} would also be  
useful.

It's not clear to me that there's much to be gained from building in  
more complex formatters for dictionary-like objects, since it will be  
hard to describe the plethora of different ways it could be done, and  
while having multi-line formatting options for long lists/sets would  
be nice it may deviate too far from the standard usage of string  
formatting, but displaying simple collections is a sufficiently  
common task that I think it's worth looking at.

	Nicko