利用python模擬sql語句對員工表格進行增刪改查
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具體需求:
員工信息表程序,實現(xiàn)增刪改查操作:
可進行模糊查詢,語法支持下面3種:
select name,age from staff_data where age > 22
多個查詢參數(shù)name,age 用','分割
select * from staff_data where dept = 人事
select * from staff_data where enroll_date like 2013
查到的信息,打印后,最后面還要顯示查到的條數(shù)
可創(chuàng)建新員工紀錄,以phone做唯一鍵,phone存在即提示,staff_id需自增,添加多個記錄record1/record2中間用'/'分割
insert into staff_data values record1/record2
可刪除指定員工信息紀錄,輸入員工id,即可刪除
delete from staff_data where staff_id>=5andstaff_id<=10
可修改員工信息,語法如下:
update staff_table set dept=Market,phone=13566677787 where dept = 運維
多個set值用','分割
使用re模塊,os模塊,充分使用函數(shù)精簡代碼,熟練使用 str.split()
來解析格式化字符串
由于,sql命令中的幾個關(guān)鍵字符串有一定規(guī)律,只出現(xiàn)一次,并且有順序!!!
按照key_lis = ['select', 'insert', 'delete', 'update', 'from', 'into', 'set', 'values', 'where', 'limit']
的元素順序分割sql.
分割元素作為sql_dic字典的key放進字典中.分割后的列表為b,如果len(b)>1,說明sql字符串中含有分割元素,同時b[0]對應上一個分割元素的值,b[-1]為下一次分割對象!
這樣不斷迭代直到把sql按出現(xiàn)的所有分割元素分割完畢,但注意這里每次循環(huán)都是先分割后賦值!!!當前分割元素比如'select'對應的值,需要等到下一個分割元素
比如'from'執(zhí)行分割后的列表b,其中b[0]的值才會賦值給sql_dic['select']
,所以最后一個分割元素的值,不能通過上述循環(huán)來完成,必須先處理可能是最后一個分割元素,再正常循環(huán)!!
在這sql語句中,有可能成為最后一個分割元素的 'limit' ,'values', 'where', 按優(yōu)先級別,先處理'limit' ,再處理'values'或 'where'.....
處理完得到sql_dic后,就是你按不同命令執(zhí)行,對數(shù)據(jù)文件的增刪改查,最后返回處理結(jié)果!!
示例代碼
# _*_coding:utf-8_*_ # Author:Jaye He import re import os def sql_parse(sql, key_lis): ''' 解析sql命令字符串,按照key_lis列表里的元素分割sql得到字典形式的命令sql_dic :param sql: :param key_lis: :return: ''' sql_list = [] sql_dic = {} for i in key_lis: b = [j.strip() for j in sql.split(i)] if len(b) > 1: if len(sql.split('limit')) > 1: sql_dic['limit'] = sql.split('limit')[-1] if i == 'where' or i == 'values': sql_dic[i] = b[-1] if sql_list: sql_dic[sql_list[-1]] = b[0] sql_list.append(i) sql = b[-1] else: sql = b[0] if sql_dic.get('select'): if not sql_dic.get('from') and not sql_dic.get('where'): sql_dic['from'] = b[-1] if sql_dic.get('select'): sql_dic['select'] = sql_dic.get('select').split(',') if sql_dic.get('where'): sql_dic['where'] = where_parse(sql_dic.get('where')) return sql_dic def where_parse(where): ''' 格式化where字符串為列表where_list,用'and', 'or', 'not'分割字符串 :param where: :return: ''' casual_l = [where] logic_key = ['and', 'or', 'not'] for j in logic_key: for i in casual_l: if i not in logic_key: if len(i.split(j)) > 1: ele = i.split(j) index = casual_l.index(i) casual_l.pop(index) casual_l.insert(index, ele[0]) casual_l.insert(index+1, j) casual_l.insert(index+2, ele[1]) casual_l = [k for k in casual_l if k] where_list = three_parse(casual_l, logic_key) return where_list def three_parse(casual_l, logic_key): ''' 處理臨時列表casual_l中具體的條件,'staff_id>5'-->['staff_id','>','5'] :param casual_l: :param logic_key: :return: ''' where_list = [] for i in casual_l: if i not in logic_key: b = i.split('like') if len(b) > 1: b.insert(1, 'like') where_list.append(b) else: key = ['<', '=', '>'] new_lis = [] opt = '' lis = [j for j in re.split('([=<>])', i) if j] for k in lis: if k in key: opt += k else: new_lis.append(k) new_lis.insert(1, opt) where_list.append(new_lis) else: where_list.append(i) return where_list def sql_action(sql_dic, title): ''' 把解析好的sql_dic分發(fā)給相應函數(shù)執(zhí)行處理 :param sql_dic: :param title: :return: ''' key = {'select': select, 'insert': insert, 'delete': delete, 'update': update} res = [] for i in sql_dic: if i in key: res = key[i](sql_dic, title) return res def select(sql_dic, title): ''' 處理select語句命令 :param sql_dic: :param title: :return: ''' with open('staff_data', 'r', encoding='utf-8') as fh: filter_res = where_action(fh, sql_dic.get('where'), title) limit_res = limit_action(filter_res, sql_dic.get('limit')) search_res = search_action(limit_res, sql_dic.get('select'), title) return search_res def insert(sql_dic, title): ''' 處理insert語句命令 :param sql_dic: :param title: :return: ''' with open('staff_data', 'r+', encoding='utf-8') as f: data = f.readlines() phone_list = [i.strip().split(',')[4] for i in data] ins_count = 0 if not data: new_id = 1 else: last = data[-1] last_id = int(last.split(',')[0]) new_id = last_id+1 record = sql_dic.get('values').split('/') for i in record: if i.split(',')[3] in phone_list: print('\033[1;31m%s 手機號已存在\033[0m' % i) else: new_record = '%s,%s\n' % (str(new_id), i) f.write(new_record) new_id += 1 ins_count += 1 f.flush() return ['insert successful'], [str(ins_count)] def delete(sql_dic, title): ''' 處理delete語句命令 :param sql_dic: :param title: :return: ''' with open('staff_data', 'r', encoding='utf-8') as r_file,\ open('staff_data_bak', 'w', encoding='utf-8') as w_file: del_count = 0 for line in r_file: dic = dict(zip(title.split(','), line.split(','))) filter_res = logic_action(dic, sql_dic.get('where')) if not filter_res: w_file.write(line) else: del_count += 1 w_file.flush() os.remove('staff_data') os.rename('staff_data_bak', 'staff_data') return ['delete successful'], [str(del_count)] def update(sql_dic, title): ''' 處理update語句命令 :param sql_dic: :param title: :return: ''' set_l = sql_dic.get('set').strip().split(',') set_list = [i.split('=') for i in set_l] update_count = 0 with open('staff_data', 'r', encoding='utf-8') as r_file,\ open('staff_data_bak', 'w', encoding='utf-8') as w_file: for line in r_file: dic = dict(zip(title.split(','), line.strip().split(','))) filter_res = logic_action(dic, sql_dic.get('where')) if filter_res: for i in set_list: k = i[0] v = i[-1] dic[k] = v line = [dic[i] for i in title.split(',')] update_count += 1 line = ','.join(line)+'\n' w_file.write(line) w_file.flush() os.remove('staff_data') os.rename('staff_data_bak', 'staff_data') return ['update successful'], [str(update_count)] def where_action(fh, where_list, title): ''' 具體處理where_list里的所有條件 :param fh: :param where_list: :param title: :return: ''' res = [] if len(where_list) != 0: for line in fh: dic = dict(zip(title.split(','), line.strip().split(','))) if dic['name'] != 'name': logic_res = logic_action(dic, where_list) if logic_res: res.append(line.strip().split(',')) else: res = [i.split(',') for i in fh.readlines()] return res pass def logic_action(dic, where_list): ''' 判斷數(shù)據(jù)文件中每一條是否符合where_list條件 :param dic: :param where_list: :return: ''' logic = [] for exp in where_list: if type(exp) is list: exp_k, opt, exp_v = exp if exp[1] == '=': opt = '==' logical_char = "'%s'%s'%s'" % (dic[exp_k], opt, exp_v) if opt != 'like': exp = str(eval(logical_char)) else: if exp_v in dic[exp_k]: exp = 'True' else: exp = 'False' logic.append(exp) res = eval(' '.join(logic)) return res def limit_action(filter_res, limit_l): ''' 用列表切分處理顯示符合條件的數(shù)量 :param filter_res: :param limit_l: :return: ''' if limit_l: index = int(limit_l[0]) res = filter_res[:index] else: res = filter_res return res def search_action(limit_res, select_list, title): ''' 處理需要查詢并顯示的title和相應數(shù)據(jù) :param limit_res: :param select_list: :param title: :return: ''' res = [] fields_list = title.split(',') if select_list[0] == '*': res = limit_res else: fields_list = select_list for data in limit_res: dic = dict(zip(title.split(','), data)) r_l = [] for i in fields_list: r_l.append((dic[i].strip())) res.append(r_l) return fields_list, res if __name__ == '__main__': with open('staff_data', 'r', encoding='utf-8') as f: title = f.readline().strip() key_lis = ['select', 'insert', 'delete', 'update', 'from', 'into', 'set', 'values', 'where', 'limit'] while True: sql = input('請輸入sql命令,退出請輸入exit:').strip() sql = re.sub(' ', '', sql) if len(sql) == 0:continue if sql == 'exit':break sql_dict = sql_parse(sql, key_lis) fields_list, fields_data = sql_action(sql_dict, title) print('\033[1;33m結(jié)果如下:\033[0m') print('-'.join(fields_list)) for data in fields_data: print('-'.join(data))
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