title: Applying uppercase to a column in pandas dataframe
body: <p>I'm having trouble applying upper case to a column in my DataFrame.</p>
  
  <p>dataframe is <code>df</code>.</p>
  
  <p><code>1/2 ID</code> is the column head that need to apply UPPERCASE.</p>
  
  <p>The problem is that the values are made up of three letters and three numbers. For example <code>rrr123</code> is one of the values.</p>
  
  <pre><code>df['1/2 ID'] = map(str.upper, df['1/2 ID'])
  </code></pre>
  
  <p>I got an error:</p>
  
  <p><code>TypeError: descriptor 'upper' requires a 'str' object but received a 'unicode' error.</code></p>
  
  <p>How can I apply upper case to the first three letters in the column of the DataFrame <code>df</code>?</p>