python算法实现3——插入排序

def insert_sort(arr): 
    arr_len = len(arr) 
    for i in range(1, arr_len): 
        for j in range(i, 0, -1):
            if arr[j] < arr[j-1]: 
                arr[j], arr[j-1] = arr[j-1], arr[j]

if __name__ == '__main__': 
    arr = [5, 4, 3, 2, 1] 
    insert_sort(arr) 
    print(arr)