Python min value in nested lists : <pre><code>a_list = [['2', 0.5],
['2', 0.5],
['2', 1.0],
['1', 2.0],
['1', 3.5],
['1', 2.5]]

b_list = {'1', '2'}
</code></pre>

<p>What is the most pythonic way of calculating the min value from a_list for each value in b_list?</p>
