def average_absolute_deviation(nums: list[int]) -> float:
 """
 Return the average absolute deviation of a list of numbers.
 Wiki: https://en.wikipedia.org/wiki/Average_absolute_deviation

 >>> average_absolute_deviation([0])
 0.0
 >>> average_absolute_deviation([4, 1, 3, 2])
 1.0
 >>> average_absolute_deviation([2, 70, 6, 50, 20, 8, 4, 0])
 20.0
 >>> average_absolute_deviation([-20, 0, 30, 15])
 16.25
 >>> average_absolute_deviation([])
 Traceback (most recent call last):
 ...
 ValueError: List is empty
 """
 if not nums: # Makes sure that the list is not empty
 raise ValueError("List is empty")

 average = sum(nums) / len(nums) # Calculate the average
 return sum(abs(x - average) for x in nums) / len(nums)


if __name__ == "__main__":
 import doctest

 doctest.testmod()