title: Sum date with integer in Python 3.x
body: <p>I have a dataframe, in which I want to create a new column which will sum two columns: </p>
  
  <pre><code>   index  Date          num  
  0      0  2004-03-09      1  
  1      1  2004-03-09      2
  2      2  2004-03-09   -300
  3      3  2004-03-09     -5
  4      4  2004-03-09      3
  </code></pre>
  
  <p>Date is in date format and num is integer. The output should look like this:</p>
  
  <pre><code>    index Date          num  Date_2 
  0      0  2004-03-09      1  2004-03-10
  1      1  2004-03-09      2  2004-03-11
  2      2  2004-03-09   -300  2003-05-14
  3      3  2004-12-09     -5  2003-12-04
  4      4  2004-02-09      3  2004-02-12
  5      5  2004-05-09      3  2004-05-12
  </code></pre>
  
  <p>This was very straightforward to do in R, but since I have just started with Python I cannot figure it out. 
  (Of course when I try to sum the columns I get an error that they are incompatible for operation)</p>
  
  <pre><code>[In]: df['Date_2'] = df['Date'] + df['num']
  
  [Out]: incompatible type for a datetime/timedelta operation [__add__]
  </code></pre>
  
  <p>I tried converting the 'num' column in days, but I was unsuccessful. </p>