Does anyone know the relation of 'key' in here?

Question

L = [3,-4,-2,5,1]
print(sorted(L,key = lambda x: abs(x)))

Answer 1

Key is the function used for sorting.
By default, it is 'lambda x: x'.
In your example, the list is sorted based on the absolute value of the elements, so the result will be [1,-2,3,-4,5].