Unique lists from a list
<p>Given a list I need to return a list of lists of unique items. I'm looking to see if there is a more Pythonic way than what I came up with:</p>

<pre><code>def unique_lists(l):
    m = {}
    for x in l:
        m[x] = (m[x] if m.get(x) != None else []) + [x]
    return [x for x in m.values()]    

print(unique_lists([1,2,2,3,4,5,5,5,6,7,8,8,9]))
</code></pre>

<p>Output:</p>

<pre><code>[[1], [2, 2], [3], [4], [5, 5, 5], [6], [7], [8, 8], [9]]
</code></pre>
