[Python-3000] PEP 3101 str.format() equivalent of '%#o/x/X'?

[Eric Smith]

Nick Coghlan wrote:
> Doing the right thing for negative numbers is a good point. It also 
> means the prefix can be handled properly when dealing with aligned 
> fields. The following update to the standard format specifier in the PEP:
> 
>   [[fill]align][#][sign][0][minimumwidth][.precision][type]
> 
>   The '#' prefix option inserts the appropriate prefix characters ('0b', 
> '0o', '0x', '0X') when displaying numbers in binary, octal or 
> hexadecimal formats. The prefix is inserted into the displayed number 
> after the sign character and fill characters (if any), but before any 
> leading zeroes.

I was implementing this today, and I note that %-formatting doesn't 
specify an order among the #, sign, and 0 flags (at least not that I 
could tell by experimentation).  PEP 3101 does say that sign comes 
before 0 for str.format().  Do we want the # to come before sign?  Do we 
want an order at all?

This sort of surprised me when I was writing tests.  Even after having 
implemented it, I was expecting "-#x" to work, but it needs to be "#-x".

I don't mind there being a fixed order (in fact I prefer it for a number 
of reasons), I just want to make sure that the order specified above is 
what we want to go with.

Eric.