trouble subclassing str

[Bengt Richter]

On 23 Jun 2005 21:27:20 -0700, "Paul McGuire" <ptmcg at austin.rr.com> wrote:

>Dang, that class should be:
>
>class PaddedStr(str):
>    def __new__(cls,s,l,padc=' '):
>        if l > len(s):
>            s2 = "%s%s" % (s,padc*(l-len(s)))
>            return str.__new__(cls,s2)
>        else: 
>            return str.__new__(cls,s) 
>
Or you could write

 >>> class PaddedStr2(str):
 ...     def __new__(cls,s,l,padc=' '):
 ...         return str.__new__(cls, s+padc*(l-len(s)))
 ...

Which gives

 >>> print '>%s<' % PaddedStr2('xxx',5,'.')
 >xxx..<
 >>> print '>%s<' % PaddedStr2('xxx',3,'.')
 >xxx<
 >>> print '>%s<' % PaddedStr2('xxx',2,'.')
 >xxx<

(Taking advantage of multipliers <=0 working like 0 for strings):

 >>> for i in xrange(-3,4): print  '%2s: >%s<'% (i, 'xxx'+'.'*i)
 ...
 -3: >xxx<
 -2: >xxx<
 -1: >xxx<
  0: >xxx<
  1: >xxx.<
  2: >xxx..<
  3: >xxx...<

Regards,
Bengt Richter