Pythonic way for calculating
<p>I have two python lists of floats (lists are of same size i.e same number of elements)</p>

<pre><code>list1 = [20, 30, 40, 50]
list2 = [1.1, 1.3, 1.7, 1.8]
</code></pre>

<p>I want to calculate <code>sum(list1[i]*list2[i])/sum(list1[i])</code> (where i goes from 0 to len(list1).</p>

<p>This can be done using for loop, but is there a better way (more pythonic way like using lambda etc..)</p>

<p>Thanks</p>
