title: operate through subarrays of an array recursively merging them (python)
body: <p>I have this question:
  if you have an array of arrays, lets say, like this</p>
  
  <pre><code>A = [[1, 2], [3, 6, 8, 1], [2, 4, 7]]
  </code></pre>
  
  <p>how is it possible to perform an operation between the first two subarrays and write the result as a new subarray which occupies the place of the two old ones so that the operation can be recursively re-computed between this new sub array and the one next to it until we only get one array?</p>