def quicksort(t):
    if t == []:
        return []
    else:
        pivot = t[0]
    t1 = []
    t2 = []
    for x in t[1:]:
        if x<pivot:
            t1.append(x)
        else:
            t2.append(x)
        return quicksort(t1) + [pivot] + quicksort(t2)

quicksort([1,4, 5])