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

#查询语句
# select name,age where age>22
# select * where job=IT
# select * where phone like 133

#读文件
def read_file():
    with open('userinfo','r') as f:
        for line in f:
            line_lst = line.strip().split(',')
            yield line_lst

#筛选
def filter_item(col,value,condition):
    dic = {'id':0,'name':1,'age':2,'phone':3,'job':4}
    correct = []#存储符合条件的行
    '''筛选条件'''
    for line_lst in read_file():
        if eval(condition):
            correct.append((line_lst))
    return correct


#分析条件
def condition_an(con):
    # 分析条件
    #根据条件中的符号来进行操作：> = < like
    if '>' in con:
        col_name,value = con.split('>')
        condition = 'int(line_lst[dic[col]]) > int(value)'
    elif '<' in con:
        col_name,value = con.split('<')
        condition = 'int(line_lst[dic[col]]) < int(value)'
    elif '=' in con:
        col_name,value = con.split('=')
        condition = 'line_lst[dic[col]] == value'
    elif 'like' in con:
        col_name,value = con.split('like')
        condition = 'value in line_lst[dic[col]]'
    correct = filter_item(col_name.strip(),value.strip(),condition)
    return correct


#输出结果
def show(col,correct):
    dic = {'id': 0, 'name': 1, 'age': 2, 'phone': 3, 'job': 4}
    result_list_final = []
    if '*' == col.strip():
        col_lst = dic.keys()
        result_list_final.append(col_lst)
    else:
        col_lst = col.split(',')
        result_list_final.append(col_lst)
    for i in correct:
        result_list = []
        for col in col_lst:
            result_list.append(i[dic[col]])
        result_list_final.append(result_list)
    return result_list_final

#结果数据展示
def information(result):
    len1 = len(result[0])
    print('+','result'.center(len1*14-3,'-'),'+')
    for i in result:
        print(end='|')
        if result.index(i)==0:
            for j in i:
                print(j.center(13,' '),end='|')
            print()
            print('+','-'*(len1*14-3),'+')
        else:
            for j in i:
                print(j.center(13,' '),end='|')
            print()
    print('+','end'.center(len1*14-3, '-'),'+')

flag=True
while flag:
    select = input('请按规则输入要查询的语句,退出程序请输入Q：')
    if select == 'Q':
        flag=False
    elif select.find('select')<0 or select.find('where')<0:
        print('语法错误')
    else:
        col,con = select.split('where') # 要显示的列,条件
        col = col.replace('select','').strip()
        correct = condition_an(con)#调用分析条件的函数
        result=show(col,correct)#调用输出结果的函数
        information(result)#调用结果数据展示函数