title: How to change a column in pandas dataframe to uppercase when it already has some uppercase values?
body: <p>I am new to Python and StackOverflow.</p>
  <p>I am trying to convert some values in a column <code>use_ab</code> of my dataframe:</p>
  <p>Here is what my column looks like:</p>
  <pre><code>df['use_ab'].value_counts()
  
  False    534167
  FALSE     15222
  True      12724
  TRUE       1023
  </code></pre>
  <p>What I want to do is convert all values in Upper case.</p>
  <p>I tried this code:</p>
  <pre><code>df['use_ab'] = df['use_ab'].str.upper()
  </code></pre>
  <p>It converts &quot;True&quot; and &quot;False&quot; into Uppercase and the rest in NaN values and gives me this output:</p>
  <pre><code>FALSE    15222
  TRUE      1023
  </code></pre>
  <p>Please help me to convert this column to Uppercase.</p>