How do I find the shortest overlapping match using regular expressions?

Question

I\'m still relatively new to regex. I\'m trying to find the shortest string of text that matches a particular pattern, but am having trouble if the shortest pattern is a sub

Answer 1

A Python loop to look for the shortest match, by brute force testing each substring from left to right, picking the shortest:

shortest = None
for i in range(len(string)):
    m = my_regex.match(string[i:])
    if m: 
        mstr = m.group()
        if shortest is None or len(mstr) < len(shortest):
            shortest = mstr

print shortest

Another loop, this time letting re.findall do the hard work of searching for all possible matches, then brute force testing each match right-to-left looking for a shorter substring:

# find all matches using findall
matches = my_regex.findall(string)

# for each match, try to match right-hand substrings
shortest = None
for m in matches:
    for i in range(-1,-len(m),-1):
        mstr = m[i:]        
        if my_regex.match(mstr):
            break
    else:
        mstr = m

    if shortest is None or len(mstr) < len(shortest):
        shortest = mstr

print shortest