Function printing correct Output and None
<p>I have defined this function that takes a word and a string of required letters and that returns True if the word uses all the required letters at least once. When I run this, it gives me the correct output but I do not understand why it also outputs 'None'.</p>

<p>Here is my code:</p>

<pre><code> def uses_all(word, allused):
    boolean = False
    for e in allused:
        if e in word:
            boolean = True
        else:
            boolean = False
            break 
    print boolean 

print uses_all('facebook', 'd')
</code></pre>

<p>Output:</p>

<pre><code>False
None
</code></pre>

<p>Comments on where I have gone wrong will be appreciated. </p>
