title: Replace string taken from another column in pandas
body: <p>I am trying to do a replace across one column of a pandas dataframe like the below.</p>
  
  <p>From:</p>
  
  <pre><code>a          b
  house      ho
  cheese     ee
  king       ng
  </code></pre>
  
  <p>To:</p>
  
  <pre><code>a        b
  use      ho
  chse     ee
  ki       ng
  </code></pre>
  
  <p>My attempt is to use:</p>
  
  <pre><code>df['a'] = df['a'].str.replace(df['b'], "")
  </code></pre>
  
  <p>but I get TypeError: 'Series' objects are mutable, thus they cannot be hashed</p>
  
  <p>I have done it by iterating row by row across the dataframe but its 200,000 rows so would take hours. Does anyone know how I can make this work?</p>