title: lookup from multiple columns pandas
body: <p>i have 2 dataframes df1 &amp; df2 as given below:</p>
  
  <p>df1:</p>
  
  <pre><code>a
  T11552
  T11559
  T11566
  T11567
  T11569
  T11594
  T11604
  T11625
  </code></pre>
  
  <p>df2:</p>
  
  <pre><code>a   b
  T11552  T11555
  T11560  T11559
  T11566  T11562
  T11568  T11565
  T11569  T11560
  T11590  T11594
  T11604  T11610
  T11621  T11625
  T11633  T11631
  T11635  T11634
  T13149  T13140
  </code></pre>
  
  <p>I want to have a new dataframe df3 where i want to search the value of df1 in df2. if the value is present in df2, i want to add new column in df1 returning True/False as shown below.</p>
  
  <p>df3:</p>
  
  <pre><code>a   v
  T11552  TRUE
  T11559  TRUE
  T11566  TRUE
  T11567  FALSE
  T11569  TRUE
  T11594  TRUE
  T11604  TRUE
  T11625  TRUE
  T11633  TRUE
  T11634  TRUE
  </code></pre>