利用python模拟sql语句对员工表格进行增删改查
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具体需求:
员工信息表程序，实现增删改查操作：
可进行模糊查询，语法支持下面3种:
select name,age from staff_data where age > 22 多个查询参数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，最后面还要显示查到的条数
可创建新员工纪录，以phone做唯一键，phone存在即提示,staff_id需自增,添加多个记录record1/record2中间用'/'分割
insert into staff_data values record1/record2
可删除指定员工信息纪录，输入员工id，即可删除
delete from staff_data where staff_id>=5andstaff_id<=10
可修改员工信息，语法如下:
update staff_table set dept=Market,phone=13566677787 where dept = 运维 多个set值用','分割
使用re模块,os模块,充分使用函数精简代码,熟练使用 str.split()来解析格式化字符串
由于,sql命令中的几个关键字符串有一定规律,只出现一次,并且有顺序!!!
按照key_lis = ['select', 'insert', 'delete', 'update', 'from', 'into', 'set', 'values', 'where', 'limit']的元素顺序分割sql.
分割元素作为sql_dic字典的key放进字典中.分割后的列表为b,如果len(b)>1,说明sql字符串中含有分割元素,同时b[0]对应上一个分割元素的值,b[-1]为下一次分割对象!
这样不断迭代直到把sql按出现的所有分割元素分割完毕,但注意这里每次循环都是先分割后赋值!!!当前分割元素比如'select'对应的值,需要等到下一个分割元素
比如'from'执行分割后的列表b,其中b[0]的值才会赋值给sql_dic['select'] ,所以最后一个分割元素的值,不能通过上述循环来完成,必须先处理可能是最后一个分割元素,再正常循环!!
在这sql语句中,有可能成为最后一个分割元素的 'limit' ,'values', 'where', 按优先级别,先处理'limit' ,再处理'values'或 'where'.....
处理完得到sql_dic后,就是你按不同命令执行,对数据文件的增删改查,最后返回处理结果!!
示例代码
# _*_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字符串为列表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):
'''
处理临时列表casual_l中具体的条件,'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分发给相应函数执行处理
: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):
'''
处理select语句命令
: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):
'''
处理insert语句命令
: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 手机号已存在\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):
'''
处理delete语句命令
: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):
'''
处理update语句命令
: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):
'''
具体处理where_list里的所有条件
: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):
'''
判断数据文件中每一条是否符合where_list条件
: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):
'''
用列表切分处理显示符合条件的数量
: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):
'''
处理需要查询并显示的title和相应数据
: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('请输入sql命令,退出请输入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结果如下:\033[0m')
print('-'.join(fields_list))
for data in fields_data:
print('-'.join(data))
总结
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