title: Check for a value from one dataframe exists in another
body: <p>I have 2 dataframes.</p>
  
  <pre><code>df1
  
  id    marks
  1      100
  2      200
  3      300
  
  
  df2
  
  name    score  flag
  'abc'    100    T
  'zxc'    300    F
  </code></pre>
  
  <p>What I am looking for is the from the first row of my df1,
  check the corresponding column <code>score</code> in my df2 , and get the Flag of that.</p>
  
  <p>i.e</p>
  
  <pre><code>row = df1.iloc[0]
  marks = row['marks']
  </code></pre>
  
  <p>find the corresponding value in marks from df2, and give what Flag it has.</p>
  
  <p>i.e 
  <code>for marks 100 ====corresponds to score 100 and flag = T</code></p>
  
  <p>I don't want to use pandas <code>merge</code>, as I only want to look for my first row. using <code>iloc[0]</code></p>