Selection sort

# Меняет первое вхождение a на b в arr
def replace_first(a, b, arr):
    arr = arr[:] 
    for i, x in enumerate(arr):
        if x == a:
            arr[i] = b
            return arr
    return arr



def selection_sort(a, i=0):
    if i == len(a) - 1:
        return a
    head, current, tail= a[:i], a[i], a[i + 1:]
    if min(tail) < current:
        return selection_sort(head + [min(tail)] + replace_first(min(tail), current, tail), i + 1)
    return selection_sort(a, i + 1)

print(selection_sort([4, 3, 2, 1]))
#[1, 2, 3, 4]