title: Impose OR on a list of conditions (masks) python pandas
body: <p>I have a dataframe of the following type:</p>
  
  <pre><code>                  dummy1  dummy2  dummy3  ...  dummy8  dummy9  dummy10
  Date       ID                             ...                        
  1998-01-01 X       1        NaN      NaN  ...     NaN     NaN     NaN
             Y       1        NaN      NaN  ...     NaN     NaN     NaN
  1998-01-02 X       NaN      NaN      NaN  ...     NaN     NaN     NaN
             Y       NaN      NaN      NaN  ...     NaN     NaN     NaN
  1998-01-05 X       NaN      NaN      NaN  ...     NaN     NaN     NaN
                     ...      ...      ...  ...     ...     ...     ...
  2016-12-27 Y       NaN        1      NaN  ...     NaN     NaN     NaN
  2016-12-28 X       NaN        1      NaN  ...     NaN     NaN     NaN
             Y       NaN      NaN      NaN  ...     NaN     NaN     NaN
  2016-12-29 X       NaN      NaN      NaN  ...     NaN     1       NaN
             Y       NaN      NaN      NaN  ...     NaN     1       NaN
  </code></pre>
  
  <p>Now, I have a list of Boolean series which correspond to specifc masks for the dataframe above which I call <code>mask</code>. This means <code>mask</code> contains several elements (in particular: one for every dummy of the dataframe) of the type of, say, <code>mask[0]</code> which is:</p>
  
  <pre><code>Date        Index
   1998-01-01  X      True
               Y      True
   1998-01-02  X     False
               Y     False
   1998-01-05  X     False
                        ...  
   2016-12-27  Y     False
   2016-12-28  X     False
               Y     False
   2016-12-29  X     False
               Y     False
  </code></pre>
  
  <p>Now, regardless of how I built the <code>mask</code> series (they are True if the corresponding dummy is 1 in the dataframe), I would like to apply the following command:</p>
  
  <pre><code>df_new=df[masks[0] | masks[1] | masks[2] | masks[3] | masks[4] | masks[5] | masks[6] | masks[7] | masks[8] | masks[9]]
  </code></pre>
  
  <p>which means I want to apply all the masks contained in the list <code>mask</code> with the OR operator, all at he same time, on my dataframe <code>df</code>. How do I do it in an 'authomatic' way without the need of manually specifying all the elements of <code>mask</code>? It is very important or me to be able to 'automize' this part as part of a function that creates a number of different <code>mask</code> elements based on the number of dummy in the columns of the dataframe</p>