Iterate individual elements in python sets

Question

Given m sets of integers that have n elements.

I have the below code, which outputs the element which occurs maximum number of times.

def find_element_which_appeared_in_max_sets(input_set):

    hash_table = {}

    # count the frequencies
    for pair in input_set:
        for i in range(0,len(pair)):
            if pair[i] in hash_table:
                hash_table[pair[i]] = hash_table[pair[i]] + 1
            else:
                hash_table[pair[i]] = 1 # first occurence

    # scan and find the element with highest frequency.
    max_freq = 0
    for elem in hash_table:

        if hash_table[elem] > max_freq:
            max_freq = hash_table[elem]
            max_occured_elem = elem

    return max_occured_elem


input_set = {(5,4),(3,2),(4,3),(8,3)}
print ""+str(find_element_which_appeared_in_max_sets(input_set))

Output:

3

Is there a more neater/elegant way of iterating through individual elements of the set?

Answer 1

You can simply use collections.Counter and itertools.chain.from_iterable, like this

def find_element_which_appeared_in_max_sets(input_set):
    return Counter(chain.from_iterable(input_set)).most_common(1)[0][0]

chain.from_iterable(input_set) will flatten out the input set of tuples to get a single iterable which gives values from each of the tuples, one by one.

Then Counter counts the number of times each and every item occurred and maintains the item and its count as a dictionary.

Then the most_common(1) call on Counter returns a list of items with top n (parameter passed to it) maximum number of occurrences, in the format (item, count). Since we are only interested in the item, we return the first item with [0][0].

Answer 2

Using only built-ins, without standard library imports:

def find_element_which_appeared_in_max_sets(input_set):
    hash_table = {}
    for pair in input_set:
        for item in pair:
            #enhanced as proposed by thefourtheye
            hash_table[item] = hash_table.get(item, 0) + 1
    max_occured_element = max(hash_table, key=hash_table.get)
    return max_occured_element