title: How to add a specific number of characters to the end of string in Pandas?
body: <p>I am using the Pandas library within Python and I am trying to increase the length of a column with text in it to all be the same length. I am trying to do this by adding a specific character (this will be white space normally, in this example I will use "_") a number of times until it reaches the maximum length of that column. </p>
  
  <p>For example:</p>
  
  <p><strong>Col1_Before</strong></p>
  
  <pre><code>A
  B
  A1R
  B2
  AABB4
  </code></pre>
  
  <p><strong>Col1_After</strong></p>
  
  <pre><code>A____
  B____
  A1R__
  B2___
  AABB4
  </code></pre>
  
  <p>So far I have got this far (using the above table as the example). It is the next part (and the part that does it that I am stuck on).</p>
  
  <pre><code>df['Col1_Max'] = df.Col1.map(lambda x: len(x)).max()
  df['Col1_Len'] = df.Col1.map(lambda x: len(x))
  df['Difference_Len'] = df ['Col1_Max'] - df ['Col1_Len']
  </code></pre>
  
  <p>I may have not explained myself well as I am still learning. If this is confusing let me know and I will clarify. </p>