--- a/trafficintelligence/tests/utils.txt	Wed Jun 20 00:07:03 2018 -0400
+++ b/trafficintelligence/tests/utils.txt	Wed Jun 20 12:04:22 2018 -0400
@@ -55,8 +55,8 @@
 'b'
 >>> mostCommon(list(range(10))+[1])
 1
->>> mostCommon([list(range(2)), list(range(4)), list(range(2))])
-[0, 1]
+>>> mostCommon([(1,2), (2,3), (1,2)])
+(1, 2)
 
 >>> res = sortByLength([list(range(3)), list(range(4)), list(range(1))])
 >>> [len(r) for r in res]

--- a/trafficintelligence/utils.py	Wed Jun 20 00:07:03 2018 -0400
+++ b/trafficintelligence/utils.py	Wed Jun 20 12:04:22 2018 -0400
@@ -6,6 +6,7 @@
 from pathlib import Path
 from math import sqrt, ceil, floor
 from copy import deepcopy, copy
+from collections import Counter
 
 from scipy.stats import rv_continuous, kruskal, shapiro, lognorm, norm, t
 from scipy.spatial import distance
@@ -747,29 +748,14 @@
 # iterable section
 #########################
 
-def mostCommon(L):
+def mostCommon(l):
     '''Returns the most frequent element in a iterable
+    The element must be hashable
 
-    taken from http://stackoverflow.com/questions/1518522/python-most-common-element-in-a-list'''
-    from itertools import groupby
-    from operator import itemgetter
-    # get an iterable of (item, iterable) pairs
-    SL = sorted((x, i) for i, x in enumerate(L))
-    # print 'SL:', SL
-    groups = groupby(SL, key=itemgetter(0))
-    # auxiliary function to get "quality" for an item
-    def _auxfun(g):
-        item, iterable = g
-        count = 0
-        min_index = len(L)
-        for _, where in iterable:
-            count += 1
-            min_index = min(min_index, where)
-            # print 'item %r, count %r, minind %r' % (item, count, min_index)
-        return count, -min_index
-    # pick the highest-count/earliest item
-    return max(groups, key=_auxfun)[0]
-
+    new version from https://stackoverflow.com/questions/41612368/find-most-common-element
+    previous version from from http://stackoverflow.com/questions/1518522/python-most-common-element-in-a-list'''
+    return Counter(l).most_common(1)[0][0]
+    
 #########################
 # sequence section
 #########################