title: Convert categorical data (in multiple columns) to binary data
body: <p>I have a categorical data (test_data) like:</p>
  
  <pre><code>s.no    Product_Category_1  Product_Category_2  Product_Category_3
  0            3                   NaN                 NaN
  1            1                    6                  14
  2            12                  NaN                 NaN
  3            12                  14                  NaN
  4            8                   NaN                 NaN
  5            1                    2                  NaN
  </code></pre>
  
  <p>I want to convert it into binary data like: </p>
  
  <pre><code>s.no    1   2   3   6    8  12   14
  0       0   0   1   0    0   0   0
  1       1   0   0   1    0   0   1
  2       0   0   0   0    0   1   0
  3       0   0   0   0    0   1   1
  4       0   0   0   0    1   0   0
  5       1   1   0   0    0   0   0
  </code></pre>
  
  <p>I could understand that I have to use one hot encoding for this. I am using python's pandas. I used the <code>get_dummies</code> function, but this function is not working on whole DataFrame. </p>