def find_largest(arr):
  """Function to find the largest number in an array
  Args:
    arr(list): The list/array to find the index

  Returns:
    largest_index(int): The index of the largest number
  """

  largest = arr[0] # stores the largest value
  largest_index = 0 # stores the position of the largest value

  for i in range(1, len(arr)):
    if arr[i] > largest:
      largest = arr[i]
      largest_index = i

  return largest_index