Selection Sort (Imperative)

selection_sort.py

def selection_sort(input_list):
    # Save the length of the list
    n = len(input_list)

    # NOTE: In Python, enumerate returns an index, value pair.
    # The _ means that we're ignoring the value.
    for current_index, _ in enumerate(input_list):
        # Save the location of the smallest item in the list
        smallest_index = current_index

        # Search the rest of the list for the smallest element
        for find_min_index in range(current_index + 1, n):
            if input_list[find_min_index] < input_list[smallest_index]:
                smallest_index = find_min_index

        # smallest_index = location of smallest element in the rest of the list
        swap(input_list, current_index, smallest_index)

    # The swap function shuffles the values of the array in-place
    return input_list


def swap(my_list, a, b):
    """
    swap is a helper method that swaps two elements in a list.
    WARNING: This operation mutates (changes) the list!
    """
    temp = my_list[a]       # save the value in position a
    my_list[a] = my_list[b] # because this line overwrites it
    my_list[b] = temp       # and use it to replace position b