Checking fuzzy/approximate substring existing in a longer string, in Python?

Question

Using algorithms like leveinstein ( leveinstein or difflib) , it is easy to find approximate matches.eg.

>>> import difflib
>>> difflib.SequenceMatcher(None,"amazing","amaging").ratio()
0.8571428571428571

The fuzzy matches can be detected by deciding a threshold as needed.

Current requirement : To find fuzzy substring based on a threshold in a bigger string.

eg.

large_string = "thelargemanhatanproject is a great project in themanhattincity"
query_string = "manhattan"
#result = "manhatan","manhattin" and their indexes in large_string

One brute force solution is to generate all substrings of length N-1 to N+1 ( or other matching length),where N is length of query_string, and use levenstein on them one by one and see the threshold.

Is there better solution available in python , preferably an included module in python 2.7 , or an externally available module .

---------------------UPDATE AND SOLUTION ----------------

Python regex module works pretty well, though it is little bit slower than inbuilt re module for fuzzy substring cases, which is an obvious outcome due to extra operations. The desired output is good and the control over magnitude of fuzziness can be easily defined.

>>> import regex
>>> input = "Monalisa was painted by Leonrdo da Vinchi"
>>> regex.search(r'\b(leonardo){e<3}\s+(da)\s+(vinci){e<2}\b',input,flags=regex.IGNORECASE)
<regex.Match object; span=(23, 41), match=' Leonrdo da Vinchi', fuzzy_counts=(0, 2, 1)>

Answer 1

How about using difflib.SequenceMatcher.get_matching_blocks?

>>> import difflib
>>> large_string = "thelargemanhatanproject"
>>> query_string = "manhattan"
>>> s = difflib.SequenceMatcher(None, large_string, query_string)
>>> sum(n for i,j,n in s.get_matching_blocks()) / float(len(query_string))
0.8888888888888888

>>> query_string = "banana"
>>> s = difflib.SequenceMatcher(None, large_string, query_string)
>>> sum(n for i,j,n in s.get_matching_blocks()) / float(len(query_string))
0.6666666666666666

---

UPDATE

import difflib

def matches(large_string, query_string, threshold):
    words = large_string.split()
    for word in words:
        s = difflib.SequenceMatcher(None, word, query_string)
        match = ''.join(word[i:i+n] for i, j, n in s.get_matching_blocks() if n)
        if len(match) / float(len(query_string)) >= threshold:
            yield match

large_string = "thelargemanhatanproject is a great project in themanhattincity"
query_string = "manhattan"
print list(matches(large_string, query_string, 0.8))

Above code print: ['manhatan', 'manhattn']