How do I find the mode of a list of numbers?

Question

I am trying to achieve this without the use of external libraries. If anyone could help me out with this and include a bit of an explanation that would be greatly appreciated.

def mode(list):
     dictionary= {}
    for i in list:
        dictionary.setdefault(i, 0)
        dictionary[i] += 1
    maximum = max(dictionary,key=dictionary.get)

You can find the frequency of each number and the number with highest frequency will be the mode. — Tanish Gupta, Sep 11 '22 at 03:13
The code you wrote looks mostly fine (apart from using `list` as an argument name), but you should `return max(dictionary, key=dictionary.get)` instead of assigning it to a variable that you never use. — Samwise, Sep 11 '22 at 03:23
Please refer to this [stackoverflow question](https://stackoverflow.com/questions/10797819/finding-the-mode-of-a-list) — jcremona, Sep 11 '22 at 03:24
I completely missed return haha. Thanks for pointing it out. — Lelefel, Sep 11 '22 at 03:32

Samwise · Answer 1 · 2022-09-11T06:19:23.927

Here's a naive (non-optimal but very simple) solution using max and count:

>>> def mode(nums):
...     return max(nums, key=nums.count)
...
>>> mode([1, 2, 3, 3, 4])
3

The more efficient solution (because it doesn't require iterating over nums once per item in nums) is indeed to use a counter. Your code mostly does this, but doesn't actually return the result:

>>> def mode(nums):
...     counter = {}
...     for i in nums:
...         counter[i] = counter.get(i, 0) + 1
...     return max(counter, key=counter.get)
...
>>> mode([1, 2, 3, 3, 4])
3

Note that the statistics module is built into Python (i.e. it is not an external library) and it contains a mode function:

>>> from statistics import mode
>>> mode([1, 2, 3, 3, 4])
3

How do I find the mode of a list of numbers?

1 Answers1