"Increment numbers in a string"

20 October 2005   2 comments   Python


Mind that age!

This blog post is 15 years old! Most likely, its content is outdated. Especially if it's technical.

I've just uploaded my second Python Cookbook recipe. It's unfortunately not rocket science but it's application is potentially very useful. With this little function you can generate the next number in a string that contains at least one number.

The mini unittest is quite interesting perhaps:

$ python increment_strings.py
from 10dsc_0010.jpg to 10dsc_0011.jpg
from dsc_9.jpg to dsc_10.jpg
from 0000001.exe to 0000002.exe
from ref-04851 to ref-04852



Looks to big for me... this will also work

import re
def increment(s):
....re.sub(r'\d+(?=[^\d]*$)', lambda m: str(int(m.group())+1).zfill(len(m.group())), s)

It's also faster. If you think it's too complex you can break it up.


slightly more readable version:

last_number = re.compile(r'\d+(?=[^\d]*$)')

def increment(string):
....def increment_number(match):
........num_str = match.group(1)
........str( int(num_str) + 1).zfill( len(num_str) )

....return last_number.sub(increment_number, string)

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