Sum numbers by letter in list of tuples
<p>I have a list of tuples: </p>

<pre><code>[ ('A',100), ('B',50), ('A',50), ('B',20), ('C',10) ]
</code></pre>

<p>I am trying to sum up all numbers that have the same letter. I.e. I want to output </p>

<pre><code>[('A', 150), ('B', 70), ('C',10)] 
</code></pre>

<p>I have tried using set to get the unique values but then when I try and compare the first elements to the set I get </p>

<pre><code>TypeError: unsupported operand type(s) for +: 'int' and 'str'
</code></pre>

<p>Any quick solutions to match the numbers by letter?</p>

<pre><code>&gt;&gt;&gt; from collections import Counter
&gt;&gt;&gt; c = Counter()
&gt;&gt;&gt; for k, num in items:
        c[k] += num


&gt;&gt;&gt; c.items()
[('A', 150), ('C', 10), ('B', 70)]
</code></pre>

<p>Less efficient (but nicer looking) one liner version:</p>

<pre><code>&gt;&gt;&gt; Counter(k for k, num in items for i in range(num)).items()
[('A', 150), ('C', 10), ('B', 70)]
</code></pre>

python list tuples