列表中重复次数最多的元素

Question

I'm trying to make a function that finds the most repeating element in a list. I thought to iterate through the list, check the count of each element and compare them(using 2 variables numnum and numnum2 )

Something's wrong, it always prints 6.

l1 = [1, 5, 7, 7, 7, 7, 7, 7, 7, 7, 1, 3, 6, 6, 3, 4, 2, 6]

print(l1)


def mostrepeating(list1=None):
    if list1 is None:
        print('No list was received in the function.')
    else:
        numnum, numnum2, result = 0, 0, 0
        for num in list1:
            if list1.index(num) == 0:
                numnum = list1.count(num)
                result = num
            else:
                numnum2 = list1.count(num)
                if numnum2 > numnum:
                    result = num
                    numnum = numnum2
        print(result)


mostrepeating(l1)

Answer 1

The problem is with if list1.index(num) == 0 , it resets results to 1, loosing the previous count. Remove it and set result to the first item in the list. To reduce iterations you should also iterate over set of the numbers

def mostrepeating(list1=None):
    if list1 is None:
        print('No list was received in the function.')
    else:
        numnum, numnum2, result = 0, 0, 0
        s = set(l1)
        result = list1[0]
        for num in s:
            numnum2 = list1.count(num)
            if numnum2 > numnum:
                result = num
                numnum = numnum2
        print(result)

Answer 2

l1 = [1, 5, 7, 7, 7, 7, 7, 7, 7, 7, 1, 3, 6, 6, 3, 4, 2, 6,6,6,6,6,6,6,6,6,6,6,6,6]

appear_dict = {}
for n in l1:
    appear_dict[n] = appear_dict.get(n, 0) + 1

most_repeat = l1[0]
for key, val in appear_dict.items():
    most_repeat = key if val > most_repeat else most_repeat

print(most_repeat)

Answer 3

You can also use the Counter class from the collections module.

>>> l1 = [1, 5, 7, 7, 7, 7, 7, 7, 7, 7, 1, 3, 6, 6, 3, 4, 2, 6]
>>> from collections import Counter
>>> Counter(l1).most_common(1)[0][0]
7

Answer 4

You can use a function wich counts all numbers in a list and puts them in a dict.

Input:

count_elements([1, 1, 1, 1, 3, 2, 5, 7, 8, 1])

Output:

{1: 5, 2: 1, 3: 1, 5: 1, 7: 1, 8: 1}

Code:

def add_element_to_dict(dictin, key):
    dictout = dictin
    if key in dictout.keys():
        dictout[key] = dictout[key] + 1
    else:
        dictout[key] = 1
    return dictout

def count_elements(list1=None):
    if list1 == None:
        print("No list specified")
        return
    else:
        numbersdict = {}
        for ele in list1:
            numbersdict = add_element_to_dict(numbersdict, ele)
    return numbersdict