我找不到任何有效的Python 3.3
mergesort算法代码，所以我自己做了一个。有什么办法可以加快速度吗？它在约0.3-0.5秒内对20,000个数字进行排序

def msort(x):
    result = []
    if len(x) < 2:
        return x
    mid = int(len(x)/2)
    y = msort(x[:mid])
    z = msort(x[mid:])
    while (len(y) > 0) or (len(z) > 0):
        if len(y) > 0 and len(z) > 0:
            if y[0] > z[0]:
                result.append(z[0])
                z.pop(0)
            else:
                result.append(y[0])
                y.pop(0)
        elif len(z) > 0:
            for i in z:
                result.append(i)
                z.pop(0)
        else:
            for i in y:
                result.append(i)
                y.pop(0)
    return result