mergesort.py

# define a mergesort function

def merge(list1, list2):
    list3 = []
    while len(list1) > 0  and len(list2) > 0:
        if list1[0] < list2[0]:
            list3.append(list1.pop(0))
        else:
            list3.append(list2.pop(0))
    if list1 == []:
        list3 += list2
    else:
        list3 += list1
    print("merged list is", list3)
    return list3


def merge_sort(unsorted):
    if len(unsorted) < 2:
        return unsorted
    else:
        middle = len(unsorted) // 2
        front = unsorted[:middle]
        back = unsorted[middle:]
        print("splits are", front, back)
        front = merge_sort(front)
        back = merge_sort(back)
    return merge(front, back)


my_list = [5,4,3,2,1]
merge_sort(my_list)