Mergesort In Python

mergesort.py

def mergesort(arr, n):
    if n == 1: return arr
    len_half = int(n/2)
    return merge(mergesort(arr[:len_half], len_half),
            mergesort(arr[len_half:], n - len_half), n)

def merge(arr1, arr2, n):
    result = []
    i,j = 0,0
    for x in range(n):
        if len(arr1) <= i:
            result.extend(arr2[j:])
            return result
        elif len(arr2) <= j:
            result.extend(arr1[i:])
            return result
        elif arr1[i] < arr2[j]:
            result.append(arr1[i])
            i += 1
        elif arr2[j] < arr1[i]:
            result.append(arr2[j])
            j += 1
    return result

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