Question

I have a two list as follows

x = ['a','a','b','c','b','a']

and

x = ['a','a','b','c','c','d']

I’m trying to find which values occur the most in each of these lists. This is what I have tried.

def unique_values(output,input):
    for i in input:
        if i not in output:
            output.append(i)
k = []
for i in k:
    unique_values(k,x)
    y.remove(i)

I’ve gotten this far but I cant figure out how to stop the for i in k: before it removes all the values in the list.

Answer 1

You can use Counter module from collections, if you want to find the occurrences of each element in the list: –

>>> x = ['a','a','b','c','c','d']

>>> from collections import Counter
>>> count = Counter(x)
>>> count
Counter({'a': 2, 'c': 2, 'b': 1, 'd': 1})
>>> count.most_common()
[('a', 2), ('c', 2), ('b', 1), ('d', 1)]

So, the first two elements are most common in your list.

>>> count.most_common()[0]
('a', 2)
>>> count.most_common()[1]
('c', 2)

or, you also pass parameter to most_common() to specify how many most-common elements you want: –

>>> count.most_common(2)
[('a', 2), ('c', 2)]

Update : –

You can also find out the max count first, and then find total number of elements with that value, and then you can use it as parameter in most_common(): –

>>> freq_list = count.values()
>>> freq_list
[2, 2, 1, 1]
>>> max_cnt = max(freq_list)
>>> total = freq_list.count(max_cnt)

>>> most_common = count.most_common(total)
[('a', 2), ('c', 2)]

>>> [elem[0] for elem in most_common]
['a', 'c']