python-作业：员工信息表

import os           #导入os模块，方便文件的删除和改名

def info_display():      #打印程序启动信息
    print("-".center(60, "-"))
    print("欢迎来到员工管理系统".center(50," "))
    print("【输入help显示帮助信息】".center(50, " "))
    print("-".center(60, "-"))
    sql = input("请输入\033[1;31msql\033[0m信息>>>>").strip("")
    if sql == "q" or sql == "quit":                #用户如果输入q，程序退出
        exit(" Bye Bye ".center(60, "-"))
    elif sql == "help":                            #用户输入help，打印help信息，help信息为打印的格式
        print("\033[1;35m 查询 输入格式：\n\tselect name,age from staff_table where age > 22\033[0m")
        print("\033[1;35m 创建 输入格式：\n\tinsert Mickle,22,13651054608,IT,2013-04-01\033[0m")
        print("\033[1;35m 修改 输入格式：\n\tupdate staff_table set dept = \"Market\" where dept = \"IT\"\033[0m")
        print("\033[1;35m 删除 输入格式：\n\tdelete 5\033[0m")
    else:
        sql_parse(sql)                              #用户输入正确的sql语法，调用sql解析函数

def sql_parse(sql):                                #对用户输入的sql语句进行解析，根据sql语句调用不同的函数
    func_choice = {"insert": insert, "delete": delete, "update": update, "select": select}
    sql_list = sql.replace(",", " ").split()  # 将sql解析成列表形式
    if sql_list[0] == "select":                   #如果用户输入的sql语句是查询
        sql_dict = {"from": [], "where": [], "limit": []}
        tag = False
        for item in sql_list:                        #根据sql解析出sql_dict
            if tag and item in sql_dict:
                tag = False
            if not tag and item in sql_dict:
                tag = True
                key = item
                continue
            if tag:
                sql_dict[key].append(item.strip(‘\"‘))
        func_choice.get(sql_list[0])(sql_dict)                  #解析出sql_dict后，传入查询函数，并调用查询函数
    elif sql_list[0] == "insert":                        #如果用户输入的sql语句是创建
        sql_dict = {}
        sql_list.remove("insert")
        sql_dict.setdefault("values",sql_list)                 #解析出sql_dict，传入创建函数
        insert(sql_dict)                                           #调用创建函数
    elif sql_list[0] == "delete":                               #解析出sql_dict后，传入删除函数，并调用查询函数
        delete_id = int(sql_list[1])                                #获取用户要删除的id
        delete(delete_id)                                       #调用删除函数
    elif sql_list[0] == "update":                                 #如果用户输入的sql语句是修改
        sql_dict = {"set":[],"where":[],"update":[]}
        tag = False
        for items in sql_list:                                #根据用户的sql，解析出sql_dict字典
            if tag and items in sql_dict:
                tag = False
            if not tag and items in sql_dict:
                tag = True
                key = items
                continue
            if tag:
                sql_dict[key].append(items.strip(‘\"‘))
        update(sql_dict)                                 #传入修改函数，并调用修改函数
    return sql_list

def insert(sql_dict):                                     #创建信息函数
    with open("staff_table","ab+") as f:
        offs = -100
        while True:
            f.seek(offs,2)
            lines = f.readlines()
            if len(lines) > 1:
                last = lines[-1]
                break
            offs *= 2
        last = last.decode(encoding="utf-8")
        last_id = int(last.split(",")[0])
        new_id = last_id + 1
        record = sql_dict.get("values")
        record.insert(0,str(new_id))
        record_str = ",".join(record)+"\n"
        f.write(bytes(record_str,encoding="utf-8"))
        f.flush()
        print("\033[1;31m创建成功 \033[0m")

def delete(delete_id):                               #删除函数
    with open("staff_table","r",encoding="utf-8") as f1,open("staff_table_bak","w",encoding=‘utf-8‘) as f2:
        del_count = 1
        for line in f1:
            if del_count != delete_id:
                f2.write(line)
            elif del_count == delete_id:
                pass
            del_count += 1
    print("\033[1;31m删除成功 \033[0m")
    os.remove("staff_table")                      #删除原员工信息文件
    os.rename("staff_table_bak","staff_table")              #修改新员工信息文件名

def update(sql_dict):                             #修改函数
    set_list = sql_dict.get("set")                   #获取要修改的内容
    set_key = set_list[0]
    where_list = sql_dict.get("where")               #获取要修改的文件内容
    with open("staff_table", "r", encoding="utf-8") as f1, open("staff_table_bak", "w", encoding=‘utf-8‘) as f2:
        for line in f1:
            title = "id,name,age,phone,dept,enroll_date"
            dic = dict(zip(title.split(","),line.split(",")))          #将文件每一行打包成字典的形式
            if logic_action(dic,where_list):                           # 逻辑判断，调用逻辑判断函数
                line = line.replace(dic[set_key],set_list[2])           #修改需要修改的那一行内容
            f2.write(line)                                              #将原文件写进新文件
    print("\033[1;31m修改成功 \033[0m")
    os.remove("staff_table")
    os.rename("staff_table_bak", "staff_table")

def select(sql_dict):                                         #查询函数
    title = "id,name,age,phone,dept,enroll_date"
    f = open("staff_table", "r", encoding="utf-8")    # 1、找到数据库
    res = []
    for line in f:
        dict1 = dict(zip(title.split(","), line.strip().split(",")))
        where_list = sql_dict.get("where")
        if len(where_list) != 0:
            if logic_action(dict1, where_list):  # 逻辑判断，调用逻辑判断函数
                res.append(line.strip())
        else:
            res = f.readlines()
    print("查询到的信息有 \033[1;35m %s \033[0m 条"%len(res))
    for i in res:
        print("分别是\033[1;35m [%s]\033[0m "%i)
    return res

def logic_action(dict1, where_list):       #逻辑判断函数，如果文件的信息符合要求，就返回True
    tag = False
    if where_list[1] == "<":
        if dict1[where_list[0]] < where_list[2]:
            tag = True
    elif where_list[1] == "=":
        if dict1[where_list[0]] == where_list[2]:
            tag = True
        else:pass
    elif where_list[1] == ">":
        if dict1[where_list[0]] > where_list[2]:
            tag = True
        else:pass
    elif where_list[1] == "like":
            if where_list[2] in dict1[where_list[0]]:
                tag = True
    return tag

while True:
    try:
        info_display()
    except IndexError as e:
        print("【%s】，请输入正确的格式"%e)              #如果用户输入的格式不正确，就打印提示