Cannot merge two dictionaries in Python
<p>I have two function which returns two dictionaries.
In third function I've tried merge these dictionaries using <code>update</code> but I've got <code>None</code>result while printing.
Could anyone explain my mistake?</p>

<pre><code>def first():
    dict1 = {
        one : [1, 2, 3]
    }
    return dict1

def second():
    dict2 = {
        two : [3, 4, 5]
    }
    return dict2

def third():
    return first().update(second)


print(third())
&gt;&gt;&gt; None
</code></pre>

<p>I also tried this way:</p>

<pre><code>def third():
    a = first().copy()
    return a.update(second())
</code></pre>

<p>By the way, this way doesn't work in Python 3.4:</p>

<pre><code>def third():
    return dict(a.items() + b.items())
</code></pre>