python归并排序

由于某人问我要个归并排序，就凑合写了一个，
AA = raw_input().split(' ')
A = [];
for num in AA:
    A.append(int(num))

def MergeSort(A):
    if len(A) <= 1:
        return A
    else:
        mid = int(len(A)/2)
        left = MergeSort(A[:mid])
        right = MergeSort(A[mid:])
        return Merge(left,right)

def Merge(left,right):
    r, l =0, 0
    result = []
    while r < len(right) and l < len(left):
        if left[l] < right[r]:
            result.append(left[l])
            l += 1
        else:
            result.append(right[r])
            r += 1
    result += left[l:]
    result += right[r:]
    return result
print MergeSort(A)