title: Check if there is a similar string in the same column
body: <p>I have a data frame like this, </p>
  
  <pre><code>df
  col1             col2
   A        'the value is zero'
   B        'this is a cat'
   C        'the value is one'
   D        'nothing is here'
   E        'the colour is blue'
   F        'this is dog'
   G        'empty sequence'
   H        'the colour is red'
   I        'the colour is green'         1
  </code></pre>
  
  <p>Now I want the similar kind of strings as flagged as 1 and others as zero, so the final data frame should look like, </p>
  
  <pre><code>col1             col2                 col1
   A        'the value is zero'           1
   B        'this is a cat'               1
   C        'the value is one'            1
   D        'nothing is here'             0
   E        'the colour is blue'          1
   F        'this is dog'                 1
   G        'empty sequence'              0
   H        'the colour is red'           1
   I        'the colour is green'         1 
  </code></pre>
  
  <p>The 0 and 1 can be obtained using SequenceMatcher(SequenceMatcher(None, s1, s2).ratio()) function and with some threshold value we can make it to zero or one.</p>
  
  <p>But if I use for loops to find the similarity between each other then it will take longer time to execute. Looking for some pandas shortcuts/pythonic way to do this efficiently.</p>