title: Filter pandas row where 1st letter in a column is/is-not a certain value
body: <p>how do I filter out a series of data (in pandas dataFrame) where I do not want the 1st letter to be 'Z', or any other character.</p>
  
  <p>I have the following pandas dataFrame, df, (of which there are > 25,000 rows).</p>
  
  <pre><code>TIME_STAMP  Activity    Action  Quantity    EPIC    Price   Sub-activity    Venue
  0   2017-08-30 08:00:05.000 Allocation  BUY 50  RRS 77.6    CPTY    066
  1   2017-08-30 08:00:05.000 Allocation  BUY 50  RRS 77.6    CPTY    066
  3   2017-08-30 08:00:09.000 Allocation  BUY 91  BATS    47.875  CPTY    PXINLN
  4   2017-08-30 08:00:10.000 Allocation  BUY 43  PNN 8.07    CPTY    WCAPD
  5   2017-08-30 08:00:10.000 Allocation  BUY 270 SGE 6.93    CPTY    PROBDMAD
  </code></pre>
  
  <p>I am trying to remove all the rows where the 1st letter of the Venue is 'Z'.</p>
  
  <p>For example, my usual filter code would be something like (filtering out all rows where the Venue = '066'</p>
  
  <pre><code>df = df[df.Venue != '066']
  </code></pre>
  
  <p>I can see this filter line filters out what I need by array, but I am not sure how to specify it within a filter context.</p>
  
  <pre><code>[k for k in df.Venue if 'Z' not in k]
  </code></pre>