#_*_coding:utf-8_*_
#第一部分:sql解析
import os
def sql_parse(sql):
'''
sql_parse--->insert_parse,delete_parse,update_parse,select_parse
sql解析總控
:param sql:用戶輸入的字符串
:return: 返回字典格式sql解析結果
'''''
parse_func={
'insert':insert_parse,
'delete':delete_parse,
'update':update_parse,
'select':select_parse,
}
sql_l=sql.split(' ')
func=sql_l[0]
res=''
if func in parse_func:
res=parse_func[func](sql_l)
return res

def insert_parse(sql_l):
# insert into db.t1 values 魯海寶,35,13910015353,測試,2005-06-27
'''
sql解析分支:insert
:param sql_l: sql按照空格分割的列表
:return: 返回字典格式的sql解析結果
'''''
sql_dic={
'func':insert, #函數名
'insert':[], #insert選項,留出擴展
'into':[], #表名
'values':[], #值
}
return handle_parse(sql_l,sql_dic)

def delete_parse(sql_l):
# delete from db.t1 where id=1
'''
sql解析分支:delete
:param sql_l: sql按照空格分割的列表
:return: 返回字典格式的sql解析結果
'''''
sql_dic={
'func':delete,
'delete':[], #delete選項,留出擴展
'from':[], #表名
'where':[], #filter條件
}
return handle_parse(sql_l,sql_dic)

def update_parse(sql_l):
# update db.t1 set id=2 where name='alex'
'''
sql解析分支:update
:param sql_l: sql按照空格分割的列表
:return: 返回字典格式的sql解析結果
'''''
sql_dic={
'func':update,
'update':[], #update選項,留出擴展
'set':[], #修改的值
'where':[], #filter條件
}
return handle_parse(sql_l,sql_dic)

def select_parse(sql_l):
# select * from db1.emp where not id= 1 and name = 'alex' or name= 'sb' limit 3
'''
sql解析分支:select
:param sql_l: sql按照空格分割的列表
:return: 返回字典格式的sql解析結果
'''''
sql_dic={
'func':select,
'select':[], #查詢字段
'from':[], #表
'where':[], #filter條件
'limit':[], #limit條件
}
return handle_parse(sql_l,sql_dic)

def handle_parse(sql_l,sql_dic):
'''
填充sql_dic
:param sql_l: sql按照空格分割的列表
:param sql_dic: 待填充的字典
:return: 返回字典格式的sql解析結果
'''''
tag=False
for item in sql_l:
if tag and item in sql_dic:
tag=False
if not tag and item in sql_dic:
tag=True
key=item
continue
if tag:
sql_dic[key].append(item)
# print('before \033[33;1m%s\033[0m' %sql_dic)
if sql_dic.get('where'):
sql_dic['where']=where_parse(sql_dic.get('where'))

# print('after \033[33;1m%s\033[0m' %sql_dic)
return sql_dic

def where_parse(where_l):
'''
對用戶輸入的where子句后的條件格式化,每個子條件都改成列表形式
:param where_l: 用戶輸入where后對應的過濾條件列表
:return:
'''''
res=[]
key=['and','or','not']
char=''
for i in where_l:
if len(i) == 0:continue
if i in key:
if len(char) != 0:
char=three_parse(char) #將每一個小的過濾條件如,name>=1轉換成['name','>=','1']
res.append(char)
res.append(i)
char=''
else:
char+=i
else:
char=three_parse(char)
res.append(char)
return res

def three_parse(exp_str):
'''
將每一個小的過濾條件如,name>=1轉換成['name','>=','1']
:param exp_str:條件表達式的字符串形式,例如'name>=1'
:return:
'''''
# print('three_opt before is \033[34;1m%s\033[0m' %exp_str)
key=['>','=','<']
res=[]
char=''
opt=''
tag=False
for i in exp_str:
if i in key:
tag=True
if len(char) !=0:
res.append(char)
char=''
opt+=i
if not tag:
char+=i
if tag and i not in key:
tag=False
res.append(opt)
opt=''
char+=i
else:
res.append(char)
# print('res is %s ' %res)
#新增like功能
if len(res) == 1:#['namelike_ale5']
res=res[0].split('like')
res.insert(1,'like')
return res


#第二部分:sql執行
def sql_action(sql_dic):
'''
執行sql的統一接口,內部執行細節對用戶完全透明
:param sql:
:return:
'''''
return sql_dic.get('func')(sql_dic)

def insert(sql_dic):
print('insert %s' %sql_dic)
db,table=sql_dic.get('into')[0].split('.')
with open('%s/%s' %(db,table),'ab+') as fh:
offs = -100
while True:
fh.seek(offs,2)
lines = fh.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
#insert into db1.emp values 張國輝,30,18500841678,運維,2007-8-1
record=sql_dic.get('values')[0].split(',')
record.insert(0,str(new_id))
#['26', 'alex', '18', '13120378203', '運維', '2013-3-1\n']
record_str=','.join(record)+'\n'
fh.write(bytes(record_str,encoding='utf-8'))
fh.flush()
return [['insert successful']]

def delete(sql_dic):
db,table=sql_dic.get('from')[0].split('.')
bak_file=table+'_bak'
with open("%s/%s" %(db,table),'r',encoding='utf-8') as r_file,\
open('%s/%s' %(db,bak_file),'w',encoding='utf-8') as w_file:
del_count=0
for line in r_file:
title="id,name,age,phone,dept,enroll_date"
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("%s/%s" % (db, table))
os.rename("%s/%s" %(db,bak_file),"%s/%s" %(db,table))
return [[del_count],['delete successful']]

def update(sql_dic):
#update db1.emp set id='sb' where name like alex
db,table=sql_dic.get('update')[0].split('.')
set=sql_dic.get('set')[0].split(',')
set_l=[]
for i in set:
set_l.append(i.split('='))
bak_file=table+'_bak'
with open("%s/%s" %(db,table),'r',encoding='utf-8') as r_file,\
open('%s/%s' %(db,bak_file),'w',encoding='utf-8') as w_file:
update_count=0
for line in r_file:
title="id,name,age,phone,dept,enroll_date"
dic=dict(zip(title.split(','),line.split(',')))
filter_res=logic_action(dic,sql_dic.get('where'))
if filter_res:
for i in set_l:
k=i[0]
v=i[-1].strip("'")
print('k v %s %s' %(k,v))
dic[k]=v
print('change dic is %s ' %dic)
line=[]
for i in title.split(','):
line.append(dic[i])
update_count+=1
line=','.join(line)
w_file.write(line)

w_file.flush()
os.remove("%s/%s" % (db, table))
os.rename("%s/%s" %(db,bak_file),"%s/%s" %(db,table))
return [[update_count],['update successful']]

def select(sql_dic):
db,table=sql_dic.get('from')[0].split('.')
fh=open("%s/%s" %(db,table),'r',encoding='utf-8')

filter_res=where_action(fh,sql_dic.get('where'))
# print('filter_res is ====>',filter_res)
fh.close()

limit_res=limit_action(filter_res,sql_dic.get('limit'))
# print('limit_res is ====>',limit_res)

search_res=search_action(limit_res,sql_dic.get('select'))
# print('select_res is ====>',search_res)

return search_res

def where_action(fh,where_l):
res=[]
logic_l=['and','or','not']
title="id,name,age,phone,dept,enroll_date"
if len(where_l) !=0:
for line in fh:
dic=dict(zip(title.split(','),line.split(',')))
logic_res=logic_action(dic,where_l)
if logic_res:
res.append(line.split(','))
else:
res=fh.readlines()
return res

def logic_action(dic,where_l):
res=[]
# print('==\033[45;1m%s\033[0m==\033[48;1m%s\033[0m' %(dic,where_l))
for exp in where_l:
if type(exp) is list:
exp_k,opt,exp_v=exp
if exp[1] == '=':
opt='%s=' %exp[1]
if dic[exp_k].isdigit():
dic_v=int(dic[exp_k])
exp_v=int(exp_v)
else:
dic_v="'%s'" %dic[exp_k]
if opt != 'like':
exp=str(eval("%s%s%s" %(dic_v,opt,exp_v)))
else:
if exp_v in dic_v:
exp='True'
else:
exp='False'
res.append(exp)
res=eval(' '.join(res))
# print('==\033[45;1m%s\033[0m' %(res))
return res

def limit_action(filter_res,limit_l):
res=[]
if len(limit_l) !=0:
index=int(limit_l[0])
res=filter_res[0:index]
else:
res=filter_res

return res

def search_action(limit_res,select_l):
res=[]
fileds_l=[]
title="id,name,age,phone,dept,enroll_date"
if select_l[0] == '*':
res=limit_res
fileds_l=title.split(',')
else:

for record in limit_res:
dic=dict(zip(title.split(','),record))
# print("dic is %s " %dic)
fileds_l=select_l[0].split(',')
r_l=[]
for i in fileds_l:
r_l.append(dic[i].strip())
res.append(r_l)

return [fileds_l,res]



if __name__ == '__main__':
while True:
sql=input("sql> ").strip()
if sql == 'exit':break
if len(sql) == 0:continue

sql_dic=sql_parse(sql)

if len(sql_dic) == 0:continue #輸入命令非法
res=sql_action(sql_dic)

for i in res[-1]:
print(i)

轉載于:https://www.cnblogs.com/changha0/p/8017829.html

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