How to add a specific number of characters to the end of string in Pandas?
<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>

<p>consider the <code>pd.Series</code> <code>s</code></p>

<pre><code>s = pd.Series(['A', 'B', 'A1R', 'B2', 'AABB4'])
</code></pre>

<p><strong><em>solution</em></strong><br>
use <code>str.ljust</code></p>

<pre><code>m = s.str.len().max()
s.str.ljust(m, '_')

0    A____
1    B____
2    A1R__
3    B2___
4    AABB4
dtype: object
</code></pre>

<hr>

<p><strong><em>for your case</em></strong>  </p>

<pre><code>m = df.Col1.str.len().max()
df.Col1 = df.Col1.ljust(m '_')
</code></pre>

python pandas dataframe string-length maxlength