Python笔记4（作业）

文件存储格式如下：
id，name，age，phone，job
1,Alex,22,13651054608,IT
2,Egon,23,13304320533,Tearcher
3,nezha,25,1333235322,IT

基础必做：
a.可以进行查询，支持三种语法：
select 列名1，列名2，… where 列名条件
支持：大于小于等于，还要支持模糊查找。
示例：
select name, age where age>22
select * where job=IT
select * where phone like 133

userinfo文件内容如下：

1,Alex,22,13651054608,IT
2,Egon,23,13304320533,Tearcher
3,nezha,25,1333235322,IT

 1 #查询语句
 2 # select name,age where age>22
 3 # select * where job=IT
 4 # select * where phone like 133
 5 
 6 #读文件
 7 def read_file():
 8     with open('userinfo','r') as f:
 9         for line in f:
10             line_lst = line.strip().split(',')
11             yield line_lst
12 
13 #筛选
14 def filter_item(col,value,condition):
15     dic = {'id':0,'name':1,'age':2,'phone':3,'job':4}
16     correct = []#存储符合条件的行
17     '''筛选条件'''
18     for line_lst in read_file():
19         if eval(condition):
20             correct.append((line_lst))
21     return correct
22 
23 
24 #分析条件
25 def condition_an(con):
26     # 分析条件
27     #根据条件中的符号来进行操作：> = < like
28     if '>' in con:
29         col_name,value = con.split('>')
30         condition = 'int(line_lst[dic[col]]) > int(value)'
31     elif '<' in con:
32         col_name,value = con.split('<')
33         condition = 'int(line_lst[dic[col]]) < int(value)'
34     elif '=' in con:
35         col_name,value = con.split('=')
36         condition = 'line_lst[dic[col]] == value'
37     elif 'like' in con:
38         col_name,value = con.split('like')
39         condition = 'value in line_lst[dic[col]]'
40     correct = filter_item(col_name.strip(),value.strip(),condition)
41     return correct
42 
43 
44 #输出结果
45 def show(col,correct):
46     dic = {'id': 0, 'name': 1, 'age': 2, 'phone': 3, 'job': 4}
47     result_list_final = []
48     if '*' == col.strip():
49         col_lst = dic.keys()
50         result_list_final.append(col_lst)
51     else:
52         col_lst = col.split(',')
53         result_list_final.append(col_lst)
54     for i in correct:
55         result_list = []
56         for col in col_lst:
57             result_list.append(i[dic[col]])
58         result_list_final.append(result_list)
59     return result_list_final
60 
61 #结果数据展示
62 def information(result):
63     len1 = len(result[0])
64     print('+','result'.center(len1*14-3,'-'),'+')
65     for i in result:
66         print(end='|')
67         if result.index(i)==0:
68             for j in i:
69                 print(j.center(13,' '),end='|')
70             print()
71             print('+','-'*(len1*14-3),'+')
72         else:
73             for j in i:
74                 print(j.center(13,' '),end='|')
75             print()
76     print('+','end'.center(len1*14-3, '-'),'+')
77 
78 flag=True
79 while flag:
80     select = input('请按规则输入要查询的语句,退出程序请输入Q：')
81     if select == 'Q':
82         flag=False
83     elif select.find('select')<0 or select.find('where')<0:
84         print('语法错误')
85     else:
86         col,con = select.split('where') # 要显示的列,条件
87         col = col.replace('select','').strip()
88         correct = condition_an(con)#调用分析条件的函数
89         result=show(col,correct)#调用输出结果的函数
90         information(result)#调用结果数据展示函数