Python：如何在字符串中搜索重复的字符串

Question

If I had a string:

x = 'ab123abc123123123123abcabcabc123123123123123123123abcabc'

What would be the best approach to print the length of the longest sequence of '123' found in a row? For this string, I would want to get 7.

I have tried using regex, but I couldn't even find a way to return the substring with two or more occurrences. I have not used regex a lot and the best I came up with is:

re.findall('123+', x)

I also tried creating a way from scratch with loops, but that also failed.

I am stuck at this point and would really appreciate any help

Answer 1

Here's one way to go about it:

x = 'ab123abc123123123123abcabcabc123123123123123123123abcabc'
index = 0
count = 0
longest = 0
while index < len (x) :
    if x [index] == '1' :
        index += 1
        if x [index] == '2' :
            index += 1
            if x [index] == '3' :
                count += 1
                if count > longest :
                    longest = count
    else : count = 0
    index += 1
print (longest)