[Python] Why does sort() with key function not do anything while sorted() is working?

I have a list of integers with duplicates and I need to sort it by the number of these duplicates.

For example:

input: n = [2, 4, 1, 2]
output: n = [4, 1, 2, 2]


I wrote some code and noticed, that sort() does not change the list. But if I try to use sorted() with the same key argument, then it works just fine. What is the reason behind this?

My code:

nums = [2, 4, 1, 2]
nums.sort(key = lambda x: nums.count(x))
print(nums)


Can it be connected to sort() method using in-place algorithm?

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