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>

<p>A one liner:</p>

<pre><code>&gt;&gt;&gt; x = [ ('A',100), ('B',50), ('A',50), ('B',20), ('C',10) ]
&gt;&gt;&gt; {
...     k: reduce(lambda u, v: u + v, [y[1] for y in x if y[0] == k])
...     for k in [y[0] for y in x]
...     }.items()
[('A', 150), ('C', 10), ('B', 70)]
</code></pre>

python list tuples