Easy way to find what item repeated in list
Question: So I have list like

    
    
     l = [1,2,3,4,4]
    

If I make a set obvilously I will get

    
    
    ([1,2,3,4])
    

I need a way to find what item repeated in list and was popped out and I do
not want to use looping. If there is an easy way to do so? I'm using python
2.7


Answer: You'll have to iterate the list, explicitly or implicitly. One way using
standard libraries would be with
[`collections.Counter`](https://docs.python.org/library/collections.html#collections.Counter):

    
    
    In [1]: from collections import Counter
    
    In [2]: l = [1,2,3,4,4]
    
    In [3]: Counter(l).most_common(1)[0][0]
    Out[3]: 4
    

* * *

A `Counter` object is a dictionary with elements of some iterable as keys and
their respective counts as values:

    
    
    In [4]: Counter(l)
    Out[4]: Counter({4: 2, 1: 1, 2: 1, 3: 1})
    

Its
[`most_common()`](https://docs.python.org/library/collections.html#collections.Counter.most_common)
method returns a list of items with highest counts:

    
    
    In [5]: Counter(l).most_common()
    Out[5]: [(4, 2), (1, 1), (2, 1), (3, 1)]
    

The optional argument restricts the length of the returned list:

    
    
    In [6]: Counter(l).most_common(1)
    Out[6]: [(4, 2)]
    

