How to get True/False mask from Pandas Series? : <p>I have a pandas Serie containing some strings</p>

<pre><code>s = pd.Series(['a', 'b', 'c', 'd', 'a'], index=[1, 2, 3, 4, 5])
</code></pre>

<p>How can I get a serie of True/False based on equality of a string?
For example I want to check the positions of all 'a' and from the example above I want to get as a result</p>

<pre><code>True, False, False, False, True
</code></pre>
