title: How to filter a pandas dataframe from start till it finds a matching string
body: <p>I have a data frame like this:</p>
  <pre><code>df:
  name    score
  Coby0    8
  Sony1    3
  Coby1    4
  Sony2    6
  Coby2    7
  Sony3    8
  Coby3    3
  Sony4    2
  Coby4    9
  Sony5    5
  Coby5    7
  Sony6    2
  Coby6    10
  </code></pre>
  <ol>
  <li>I want to filter this data frame from the start till it finds the first row that starts with 'Sony'</li>
  </ol>
  <blockquote>
  <pre><code>name    score
  Coby0    8
  Sony1    3
  </code></pre>
  </blockquote>
  <ol start="2">
  <li>I want to filter this data from the start till it finds the last row that starts with 'Sony'</li>
  </ol>
  <blockquote>
  <pre><code>df:
  name    score
  Coby0    8
  Sony1    3
  Coby1    4
  Sony2    6
  Coby2    7
  Sony3    8
  Coby3    3
  Sony4    2
  Coby4    9
  Sony5    5
  Coby5    7
  Sony6    2
  </code></pre>
  </blockquote>
  <p>Thanks in advance!</p>