python 冒泡排序

a=[1,2,3,4,5,6,7,8,9]

for j in range(len(a)):
    count = 0
    for i in range(len(a)-j-1):
        if a[i] > a[i+1]:
            a[i], a[i+1] =a[i+1], a[i]
            count+=1
    if count == 0:　　　　#count为0表示没有进行交换，列表已经有序，无需继续循环
        break
print(a)