filtering a list of tuples in python
<p>Am looking for a clean pythonic way of doing the following</p>

<p>I have a list of tuples say :</p>

<pre><code>[(1,'a'), (1,'b'), (1,'c'), (2, 'd'), (5, 'e'), (5, 'f')]
</code></pre>

<p>I want to make a new list which discards tuples whose first key has been seen before. So the o/p for the above would be:</p>

<pre><code>[(1,'c'), (2,'d'), (5, 'f')]
</code></pre>

<p>Thanks!</p>
