s5_day9作业

# 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
tesla 100000 1
mac 3000 2
lenovo 30000 3
chicken 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