[Tutor] removing padded numbers

[Kent Johnson]

Christopher Spears wrote:
> Does anyone how to remove padded numbers with python? 
> I want to be able to take a file like
> 
> afile.0001.cin
> 
> and convert it to
> 
> afile.1.cin

The straightforward way is just to pick it apart and put it back 
together the way you want it:

 >>> a, b, c = 'afile.0001.cin'.split('.')
 >>> '%s.%s.%s' % (a, b.lstrip('0'), c)
'afile.1.cin'

Or if you prefer, here is an obscure one-liner using the ability of 
re.sub() to take a callable as the replacement argument. (That is a 
pretty cool feature but overkill here...) This one replaces any run of 
digits with the same digits with leading zeros removed:

 >>> import re
 >>> re.sub(r'\d+', lambda m: m.group().lstrip('0'), 'afile.0001.cin')
'afile.1.cin'

Kent