title: pandas drop duplicate row value from a specific column
body: <p>I want to remove the duplicate row value from a specific column - in this case the column name is "number".</p>
  
  <p>Before:</p>
  
  <pre><code>        number qty status
      0    10      2    go
      1    10      5    nogo
      2    4       6    yes
      3    3       1    no
      4    2       7    go
      5    5       2    nah
      6    5       6    go
      7    5       3    nogo
      8    1       10   yes
      9    1       10   go 
      10   5       2    nah
  </code></pre>
  
  <p>After:   </p>
  
  <pre><code>        number qty status
      0    10      2    go
                   5    nogo
      1    4       6    yes
      2    3       1    no
      3    2       7    go
      4    5       2    nah
                   6    go
                   3    nogo
      5    1       10   yes
                   10   go 
      6    5       2    nah
  </code></pre>