= for fuzzy matches
mrabarnett opened this issue · 11 comments
Original report by Anonymous.
= operator could be pretty handy for fuzzy matches, finding only erroneous text. For example, in a list of hotmail email accounts, you could search for misspells like '@(hotmail.com){e=1}'. This will save the user an extra "grep -v" for filtering out correct emails in the list of matches.
Original comment by Anonymous.
or even something like this would be more powerful:
'@(hotmail\.com){0<e<3}'
matching only texts with 1 or 2 errors
Original comment by Anonymous.
A regex such as:
@(hotmail\.com){e=1}
can be we written as:
@(?>(hotmail\.com){e<=1})(?<!@hotmail\.com)
although that's not quite as convenient, I admit! :-)
Note that the fuzzy part needs to be in an atomic group in order to stop it backtracking to find a worse match. For example, given the string "@hotmail.comb", the fuzzy part will match "@hotmail.com" with 0 errors, then the negative look-behind will reject it, so the fuzzy part will match "@hotmail.comb" with 1 error.
I'm not sure how easy it'll be to add a lower limit; such a problem could still occur.
Original comment by Anonymous.
I think I've figured out how to do it, but how much demand is for it? You gave an example, but is that a real use case?
Original comment by Anonymous.
I am fixing tags for 25k+ text documents for a web site, so I do have a real (different) use case. That was just an example. But I think it would be a really nice feature for regex module...
Original comment by Anonymous.
Could you provide a few test cases?
Original comment by Anonymous.
here is a real example translated into english
3 servic detection
1 service detect
5 service detecti
46 service detection
1 in service detection
The site has manually entered tags, and their frequencies from 25k+ (non-english) text documents. Most of the time the correct one has a high frequency, and anything that is close enough to a correct one (except itself) should probably get fixed..
Original comment by Anonymous.
What fuzzy regex would you use to match the incorrect strings in your example? Would it be this:
(?:^\d+ service detection$){1<=e<=3}
Original comment by Anonymous.
no no, the first part is the frequency of a tag, not part of it. I would search a match with:
r = compile(r'(?:service detection){0<e<5}')
m = r.match(str)
if m:
Original comment by Anonymous.
or '(?:service detection){0<e<5}$' is also a possibility..
Original comment by Anonymous.
Added in regex 0.1.20120119.
Note that it supports only constraints of the form e<=3 or 1<=e<=3 ("<" is also allowed), but not "=".
Original comment by Anonymous.
thanks ^_^