[Python-Dev] [format] Restrict fill characters for numerical values (original) (raw)

Stefan Krah stefan-usenet at bytereef.org
Wed Nov 11 14:06:34 CET 2009

Eric Smith <eric at trueblade.com> wrote:

Stefan Krah wrote: >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'.

Why? What problem are you trying to prevent that would justify the extra code to implement this and the extra documentation to explain it?

I simply think that apart from rounding, the output of format should not change the numerical value of its argument. The format functions in C do not allow this to happen. Are there other languages where this is possible?

Stefan Krah

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