Python冒泡排序实现

def bubble_sort(num):
    for i in range(len(num)-1):
        for j in range(len(num)-1-i):
            if(num[j]>num[j+1]):
                tem=num[j]
                num[j]=num[j+1]
                num[j+1]=tem
    return num
a=[7,5,3,1,9,4]
bubble_sort(a)
print(a)