Python Merge Sort

merge-sort.py

def merge_sort(array: List) -> List:
    if len(array) < 2:
        return array

    middle = floor(len(array)/2)
    left = merge_sort(array[:middle])
    right = merge_sort(array[middle:])

    sorted_array = []

    while len(left) and len(right):
        if left[0] < right[0]:
            sorted_array.append(left.pop(0))
        else:
            sorted_array.append(right.pop(0))

    return sorted_array + left + right