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DDR
Asked: 2020-03-30 09:17:34 +0800 CST 2020-03-30 09:17:34 +0800 CST

How to find the most repeated number in a list?

  • 772

I have the following list:

[0, 1, 2, 3, 4, 6, 6, 17, 16, 9, 10, 23, 12, 13, 14, 15, 16, 17, 18, 4, 20, 4, 22, 23, 24, 4, 4]

I wanted to know how to find the number with the most repetitions without using a cycle since I don't see this as very practical, especially with very long lists. My idea was to use a dictionary whose elements have those of the list and here if you check the number with more repetitions through a for, however it is a process that can be very long but can be effective; and the last idea was to use the function countin a loop that checks each element of the list set.

Is there a more efficient way to solve this problem? Any ideas?

Thank you!

python

4 Answers

  1. Best Answer

    Good morning, could you try it with the statistics library?

    from statistics import mode
x = [0, 1, 2, 3, 4, 6, 6, 17, 16, 9, 10, 23, 12, 13, 14, 15, 16, 17, 18, 4, 20, 4, 22, 23, 24, 4, 4]
print(mode(x))

# 4
    • 14

  2. With base Python, you have a few alternatives:

    from collections import Counter

lista = [0, 1, 2, 3, 4, 6, 6, 17, 16, 9, 10, 23, 12, 13, 14, 15, 16, 17, 18, 4, 20, 4, 22, 23, 24, 4, 4]

print(Counter(lista).most_common()[0][0])

    The object Counter()creates a list of tuples with each element and the number of occurrences, and the [ method most_common()][2]of returns that list sorted by occurrences from highest to lowest.

    Another less performant but more compact way of writing is:

    print(max(set(lista), key=lista.count))

    Here we generate a setwhich is the set of the unique elements of the list, and we apply a max()using a method of all list count(elemento)which returns us the amount of elementoin the list.

    • 7

  3. A possible solution is to use Counter:

    from collections import Counter

l = [0, 1, 2, 3, 4, 6, 6, 17, 16, 9, 10, 23, 12, 13, 14, 15, 16, 17, 18, 4, 20, 4, 22, 23, 24, 4, 4]
c = Counter(l)
print(max(c, key=c.get))

    Output:

    4
    • 5

  4. Another option is the "scipy" library.

    Advantage: Counts the number of times the number is repeated.

    Disadvantage: You have to import numpy which is another module.

    from scipy import stats
from numpy import np

    a = [0, 1, 2, 3, 4, 6, 6, 17, 16, 9, 10, 23, 12, 13, 14, 15, 16, 17, 18, 4, 20, 4, 22, 23, 24, 4, 4]

    moda, count = stats.mode(np.array(a))

    print(moda)
[4]
print(count)
[5]
    • 2