Elegant mergesort

mergesort.txt

def merge(L, R):
    arr = []
    while len(R) and len(L):
        left = L.pop(0)
        right = R.pop(0)
        if left < right:
            arr.append(left)
            R.insert(0, right)
        else:
            arr.append(right)
            L.insert(0, left)
    arr += L if len(L) else R

    return arr


def sort(arr):
    if len(arr) > 1:
        mid = len(arr)//2
        L = sort(arr[:mid])
        R = sort(arr[mid:])
        arr = merge(L, R)
    return arr
    
if __name__ == "__main__":
    arr = [5, 6, 3, 2, 8, 1, 7, 4]
    arr = sort(arr)
    print(arr)