[Python-Dev] [format] Restrict fill characters for numerical values

[Stefan Krah]

Hi,

I think http://www.python.org/dev/peps/pep-3101/ is too liberal with the
choice of fill characters for numerical values. As far as I can see, this
is quite legal:


Python 2.7a0 (trunk:76132M, Nov  6 2009, 15:20:35) 
[GCC 4.1.3 20080623 (prerelease) (Ubuntu 4.1.2-23ubuntu3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from decimal import *
>>> format(Decimal(4), "9<10")
'4999999999'
>>> format(Decimal(4), "9>10")
'9999999994'
>>> format(Decimal(4), "->2")
'-4'
>>> 


I propose to disallow digits and '+-' fill characters for numerical values,
except for the combination '0, left-padding'. Actually, I'd prefer to allow
only whitespace and '0, left-padding'.


See also:

http://bugs.python.org/issue6871
http://bugs.python.org/issue6902



Stefan Krah