Recursive Mergesort in Python

mergesort.py

def merge(left, right):
	if not len(left) or not len(right):
		return left or right

	result = []
	i, j = 0, 0
	while (len(result) < len(left) + len(right)):
		if left[i] < right[j]:
			result.append(left[i])
			i+= 1
		else:
			result.append(right[j])
			j+= 1
		if i == len(left) or j == len(right):
			result.extend(left[i:] or right[j:])
			break 

	return result

def mergesort(list):
	if len(list) < 2:
		return list

	middle = len(list)/2
	left = mergesort(list[:middle])
	right = mergesort(list[middle:])

	return merge(left, right)

if __name__ == "__main__":
	print mergesort([3,4,5,1,2,8,3,7,6])

Thank you for this piece of code)
By the way, if someone find it interesting, here is merge realisation with deque from python collections:

from collections import deque
from itertools import islice


def merge(a, b):
    c = deque([])
    while a and b:
        i = a[0]
        j = b[0]
        if i <= j:
            c.append(i)
            a.popleft()
        else:
            c.append(j)
            b.popleft()
    if a:
        c.extend(a)
    if b:
        c.extend(b)
    return c


def merge_sort(A):
    if len(A) < 2:
        return A
    m = len(A) // 2
    l = merge_sort(deque(islice(A, 0, m)))
    r = merge_sort(deque(islice(A, m, len(A))))
    return merge(l, r)


if __name__ == '__main__':
    print(merge_sort([3, 4, 5, 1, 2, 8, 3, 7, 6]))

Here is merge sort in one function with detailed information on running process

def merge_sort(nlist):
    print("Splitting ", nlist)
    if len(nlist) > 1:
        mid = len(nlist) // 2
        lefthalf = nlist[:mid]
        righthalf = nlist[mid:]
        merge_sort(lefthalf)
        merge_sort(righthalf)
        i = j = k = 0
        while i < len(lefthalf) and j < len(righthalf):
            if lefthalf[i] < righthalf[j]:
                nlist[k] = lefthalf[i]
                i = i + 1
            else:
                nlist[k] = righthalf[j]
                j = j + 1
            k = k + 1

        while i < len(lefthalf):
            nlist[k] = lefthalf[i]
            i = i + 1
            k = k + 1

        while j < len(righthalf):
            nlist[k] = righthalf[j]
            j = j + 1
            k = k + 1
    print("Merging ", nlist)