title: Why is the IF condition being evaluated to True all the time
body: <p>Why the if statement being evaluated to <code>True</code> each time, even if I am deliberately giving biased inputs to my code . Here is my code:</p>
  
  <pre><code>s1 = 'efgh'
  s2 = 'abcd'
  
  for i in range(0, len(s1)):
      for j in range(1, len(s1)+1):
          if s1[i:j] in s2:
              print('YES')
  </code></pre>
  
  <p>It print <code>YES</code>, 6 times. Why is that?</p>