title: Merge multiple rows with same value into one row in pandas
body: <p>I have seen that there are similar questions, but the answers did not quite fit my exact needs. I have a dataframe that contains rows with different values. Some of the rows however have exactly the same value.   </p>
  
  <pre><code>     Column1 Column2 Column3
  0       a       x       x
  1       a       x       x
  2       a       x       x
  3       d       y       y
  4       d       y       y
  </code></pre>
  
  <p>What I would like to have is:</p>
  
  <pre><code>     Column1 Column2 Column3
  0       a       x       x
  1       d       y       y
  </code></pre>
  
  <p>So basically I want to merge all rows with the same values in all columns into one row. What is the most decent way to do that in python? </p>
  
  <p>Thank you in advance!</p>