http://code.activestate.com/recipes/langs/python/tags/largest/2009-04-07T18:57:35-07:00ActiveState Code Recipes2009-04-07T18:57:35-07:00George Sakkishttp://code.activestate.com/recipes/users/2591466/http://code.activestate.com/recipes/576712-handling-ties-for-top-largestsmallest-elements/

<p style="color: grey"> Python recipe 576712 by <a href="/recipes/users/2591466/">George Sakkis</a> (<a href="/recipes/tags/heapq/">heapq</a>, <a href="/recipes/tags/largest/">largest</a>, <a href="/recipes/tags/smallest/">smallest</a>, <a href="/recipes/tags/top/">top</a>). Revision 8. </p> <p>The heapq module provides efficient functions for getting the top-N smallest and largest elements of an iterable. A caveat of these functions is that if there are ties (i.e. equal elements with respect to the comparison key), some elements may end up in the returned top-N list while some equal others may not:</p> <pre class="prettyprint"><code>&gt;&gt;&gt; nsmallest(3, [4,3,-2,-3,2], key=abs) [-2, 2, 3] </code></pre> <p>Although 3 and -3 are equal with respect to the key function, only one of them is chosen to be returned. For several applications, an all-or-nothing approach with respect to ties is preferable or even required.</p> <p>A new optional boolean parameter 'ties' is proposed to accomodate these cases. If ties=True and the iterable contains more than N elements, the length of the returned sorted list can be lower than N if not all ties at the last position can fit in the list:</p> <pre class="prettyprint"><code>&gt;&gt;&gt; nsmallest(3, [4,3,-2,-3,2], key=abs, ties=True) [-2, 2] </code></pre>