How to get the "longest possible" match with Python's RE module?

[gatti at dsdata.it]

Licheng Fang wrote:

> Another question: my task is to find in a given string the substrings
> that satisfies a particular pattern. That's why the first tool that
> came to my mind is regular expression. Parsers, however, only give a
> yes/no answer to a given string. To find all substrings with a
> particular pattern I may have to try every substring, which may be an
> impossible task.

You can collect all successful parser results beginning from each index
in the string; this gives you all matches with that first index.
You could extend to multiple results general bottom-up context-free
language parsing like Earley or Tomita's algorithms; for reasonable
languages most locations can be excluded for most rules at the
beginning, with great performance improvements over trying over and
over again.

Lorenzo Gatti