title: Replace values from one column to another using pandas?
body: <p>I have a dataframe:</p>
  
  <pre><code>       subtracted      Subs        hrs  
  0      281871.120   450878.77      0.00    
  1      221343.432   229535.34      0.00     
  2      197454.408    32080.93      0.00    
  3      41934.000    -9853.07     32080.93
  </code></pre>
  
  <p>i want to replace positive values (With respect to Subs column) from subtracted column to hrs column.</p>
  
  <p>Expected output:</p>
  
  <pre><code>       subtracted      Subs        hrs  
  0      281871.120   450878.77      281871.120   
  1      221343.432   229535.34      221343.432    
  2      197454.408    32080.93      197454.408    
  3      41934.000    -9853.07       32080.93
  </code></pre>
  
  <p>Can anybody suggest me the correct way to do it?</p>