[daveguy]

That is a neat trick, but it would be incredibly brittle. Kids, don't try this at home!

[solaxun]

Pass in an re.match or re.search based function, i would imagine that would be powerful enough to meet most needs.

import re

x = ['foo12901','fooo900','fooooooo980090']

x =sorted(x,key = lambdax:int(re.search('\d+',x).group()))

print(x)

[shoyer]

+1 this is the right way to build a custom sorting function. The only thing worse than relying on ad-hoc heuristics for processing your data is relying on heuristics that somebody else maintains!