Python : list of strings to list of unique characters : <p>I have a list of strings </p>

<pre><code>ll = ['abc', 'abd', 'xyz', 'xzk']
</code></pre>

<p>I want a list of unique characters across all strings in the given list. </p>

<p>For ll, output should be </p>

<pre><code>['a','b','c','d','x','y','z','k']
</code></pre>

<p>is there a clean way to do this ?</p>
