用python语言如何排大小

a = [123, 21, 35, 65, 84, 99, 87, 546]

for y in range(0, 7):

    for i in range(0, len(a)-1):

        if a[i] < a[i+1]:

            b = a[i]

            a[i] = a[i+1]

            a[i+1] = b

print(a)