# 1 编写 tail -f a.txt |grep ‘error‘ |grep ‘404‘命令，周一默写# import time# def tail(filepath,encoding=‘utf-8‘):#     with open(filepath,encoding=encoding)as f:#         f.seek(0,2)#         while True:#             line=f.readline()#             if line:#                 yield line#             else:#                 time.sleep(0.5)# def grep(lines,pattern):#     for line in lines:#         if pattern in line:#             # print(line)#             yield line# g=tail(‘a.txt‘)# g2=grep(g,‘error‘)# g3=grep(g2,‘404‘)# for i in g3:#     print(i)# 2 文件a.txt内容# apple 10 3# tesla 100000 1# mac 3000 2# lenovo 30000 3# chicken 10 3# with open(‘a.txt‘,‘w‘,encoding=‘utf-8‘)as f:#     f.write(‘apple 10 3\ntesla 100000 1\nmac 3000 2\nlenovo 30000 3\nchicken 10 3‘)# 要求使用列表解析，从文件a.txt中取出每一行，做成下述格式# [{‘name’:‘apple‘,‘price‘:10,‘count‘:3},{...},{...},...]# with open(‘a.txt‘, ‘r‘, encoding=‘utf-8‘)as f:    # print([{‘name‘:line.strip().split()[0],‘price‘:line.strip().split()[1],‘count‘:line.strip().split()[2]} for line in f])    # for i in [{‘name‘:line.strip().split()[0],‘price‘:line.strip().split()[1],‘count‘:line.strip().split()[2]} for line in f]:    #     print(i)# 3 格式与2一样，但只保留价格大于1000的商品信息# with open(‘a.txt‘,encoding=‘utf-8‘)as f:#     for i in [{‘name‘:line.strip().split()[0],‘price‘:line.strip().split()[1],‘count‘:line.strip().split()[2]} for line in f]:#         if int(i[‘price‘])>1000:#             print(i)# 4 周末大作业（见图）：#     只实现作业要求的查询功能#     增加，删除，修改功能为选做题