title: Python - Finding elements in a list efficiently
body: <p>I have a list, list_a, that contains floating numbers:</p>
  
  <pre><code>list_a = [[[ 0 for i in range(40)] for j in range(1000)]for k in range(47)]
  </code></pre>
  
  <p>And I have a sorted version of this:</p>
  
  <pre><code>list_a_sorted = list_a
  list_a_sorted[0].sort()
  </code></pre>
  
  <p>So list_a_sorted is sorted and contains values for list_a starting from the lowest first. Let's assume it is as follows:</p>
  
  <pre><code>[2.3,3.1.........9]
  </code></pre>
  
  <p>So 2.3 is the lowest value but how can I find out if this was the 8th element in list_a or the 15th or nth?</p>
  
  <p>As my lists are quite large, I also need to do this as efficiently as possible? Any help would be appreciated, thanks</p>