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 1

You'll have to iterate the list, explicitly or implicitly. One way using standard libraries would be with 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

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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() 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)]