title: Compare columns of a CSV file using Python
body: <p>I have a CSV file as such</p>
  
  <pre><code>ID  OLD_A  NEW_A  OLD_B     NEW_B     OLD_C  NEW_C
  1   0      0      1/1/2017  1/1/2017  ABC    BCD
  2   0      0      1/1/2017  2/1/2017  ABC    ABC
  3   1      2      1/1/2017  1/1/2017  ABC    BCD
  </code></pre>
  
  <p>I want to compare the old and new columns for A,B and C and in case there's a difference in the value of OLD and NEW (there's 10k+ rows) , I want return an output as such (from above example):</p>
  
  <pre><code>ID Field_Changed OLD_Value   NEW_Value
  1  C             ABC         BCD
  2  B             1/1/2017    2/1/2017
  3  A             1           2
  3  C             ABC         BCD
  </code></pre>
  
  <p>So far I've used the .loc method of pandas.DataFrame which returns the indexed location of the rows that qualify the boolean indexing, but I need the values as well...</p>
  
  <pre><code>df.loc[(df['OLD_A'] != df['NEW_A'])].index)
  </code></pre>
  
  <p>I'm new to python scripting and cannot seem to figure the logic out. Can someone help please?</p>