title: How to remove all characters after a given character in a column dataframe with Python
body: <p>example:</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  data = {'state': ['Auckland', 'Otago (....)','Wellington','Dunedin','Hamilton'],'year': [2000, 2001, 2002, 2001,2002],'pop': [1.5, 1.7,3.6, 2.4, 2.9]}
  df = pd.DataFrame(data) 
  </code></pre>
  
  <p>I want to remove all that occur after the string <strong>'('</strong> in the state column.</p>
  
  <p>Many thanks for your help.</p>
  
  <p>Samir</p>