possible wrong result for difflib.SequenceMatcher.ratio()

[nalza001]

BPO	45180
Nosy	@tim-one

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-09-16.05:02:23.068>
created_at = <Date 2021-09-13.04:02:54.878>
labels = ['type-bug', '3.8', '3.9', '3.10', '3.11', 'invalid', '3.7', 'library']
title = 'possible wrong result for difflib.SequenceMatcher.ratio()'
updated_at = <Date 2021-09-16.05:02:23.067>
user = 'https://bugs.python.org/nalza001'

bugs.python.org fields:

activity = <Date 2021-09-16.05:02:23.067>
actor = 'tim.peters'
assignee = 'none'
closed = True
closed_date = <Date 2021-09-16.05:02:23.068>
closer = 'tim.peters'
components = ['Library (Lib)']
creation = <Date 2021-09-13.04:02:54.878>
creator = 'nalza001'
dependencies = []
files = []
hgrepos = []
issue_num = 45180
keywords = []
message_count = 6.0
messages = ['401683', '401685', '401912', '401915', '401916', '401920']
nosy_count = 2.0
nosy_names = ['tim.peters', 'nalza001']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45180'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']

[nalza001]

The difflib.SequenceMatcher.ratio() gives 0.3 instead of 1.0 or at least 0.9 for the following two strings a and b: 
a="""
#include <iostream>
#include <string>
using namespace std;
int main() {
   string userWord;
   unsigned int i;
      cin >> userWord;

      
      for(i = 0; i < userWord.size(); i++) {
         if(userWord.at(i) == 'i') {
            userWord.at(i) = '1';
         }
         if(userWord.at(i) == 'a') {
            userWord.at(i) = '@'; 
         }
         if(userWord.at(i) == 'm') {
            userWord.at(i) = 'M';
         }
         if(userWord.at(i) == 'B') {
            userWord.at(i) = '8';
         }
         if(userWord.at(i) == 's') {
            userWord.at(i) = '$';
         }
         userWord.push_back('!');
      }
      cout << userWord << endl;
   return 0;
}
"""

b="""
#include <iostream>
#include <string>
using namespace std;
int main() {
   string userWord;
   unsigned int i;
      cin >> userWord;
      userWord.push_back('!');
      
      for(i = 0; i < userWord.size(); i++) {
         if(userWord.at(i) == 'i') {
            userWord.at(i) = '1';
         }
         if(userWord.at(i) == 'a') {
            userWord.at(i) = '@'; 
         }
         if(userWord.at(i) == 'm') {
            userWord.at(i) = 'M';
         }
         if(userWord.at(i) == 'B') {
            userWord.at(i) = '8';
         }
         if(userWord.at(i) == 's') {
            userWord.at(i) = '$';
         }
   
      }
      cout << userWord << endl;
   return 0;
}
"""