python db类用法说明

import pymysql
class DB:
__host = 'localhost' # 服务器地址
__username = 'root' # 用户名
__password = '' # 密码
__database = 'test' # 数据库
__field = '*' # 查询字段
__where = '' # 条件
__sql = False # 是否返回sql
__join = '' # 联表
__order = '' # 排序
__limit = '' # 数量
# 构造函数，在生成对象时调用
def __init__(self, table):
try:
# 打开数据库连接 host, username, password, database
self.db = pymysql.connect(self.__host, self.__username, self.__password, self.__database)
except Exception as e:
print(e)
exit()
# 使用 cursor() 方法创建一个游标对象 cursor
self.cursor = self.db.cursor()
self.table = table
# 析构函数，释放对象时使用
def __del__(self):
try:
# 关闭数据库连接
self.db.close()
except Exception as e:
print(e)
# 得到当前sql语句
def getSql(self):
self.__sql = True
return self
# 字段
def field(self, str):
self.__field = str
return self
# 联表
def join(self, table, where):
self.__join = ' LEFT JOIN ' + table + ' ON ' + where + ' '
return self
# 条件
def where(self, param):
self.__where = ' WHERE '
if isinstance(param, list):
for i in param:
if isinstance(i[2], list):
tmp = '('
for j in i[2]:
tmp += str(j) + ','
tmp += ')'
self.__where += '`' + i[0] + '` ' + i[1] + ' ' + tmp + ' AND '
else:
self.__where += '`' + i[0] + '` ' + i[1] + ' ' + str(i[2]) + ' AND '
else:
self.__where = self.__where[0:-4]
else:
self.__where += param
return self
# 排序
def order(self, str):
self.__order = ' ORDER BY ' + str
return self
# 数量
def limit(self, str):
self.__limit = ' LIMIT ' + str
return self
# 增加
def insert(self, dict):
key = value = ''
for k, v in dict.items():
key += '`' + k + '`,'
value += '"' + v + '",'
key = key[0:-1]
value = value[0:-1]
sql = 'INSERT INTO ' + self.table + ' (' + key + ') VALUES (' + value + ')'
if self.__sql:
return sql
try:
# 执行sql语句
ret = self.cursor.execute(sql)
# 提交到数据库执行
self.db.commit()
return ret
except Exception as e:
# 如果发生错误则回滚
self.db.rollback()
print(e)
return 0
# 删除
def delete(self):
if self.__where:
sql = "DELETE FROM " + self.table + self.__where
if self.__sql:
return sql
try:
# 执行sql语句
ret = self.cursor.execute(sql)
# 提交到数据库执行
self.db.commit()
return ret
except Exception as e:
# 如果发生错误则回滚
self.db.rollback()
print(e)
return 0
else:
raise BaseException('没有条件') # 抛异常
# 修改
def update(self, dict):
str = ''
for k, v in dict.items():
str += '`' + k + '`="' + v + '",'
str = str[0:-1]
sql = 'UPDATE ' + self.table + ' SET ' + str
if self.__where:
sql += self.__where
if self.__sql:
return sql
try:
# 执行sql语句
ret = self.cursor.execute(sql)
# 提交到数据库执行
self.db.commit()
return ret
except Exception as e:
# 如果发生错误则回滚
self.db.rollback()
print(e)
return 0
# 查询
def select(self):
sql = "SELECT " + self.__field + " FROM " + self.table
if self.__join:
sql += self.__join
if self.__where:
sql += self.__where
if self.__order:
sql += self.__order
if self.__limit:
sql += self.__limit
if self.__sql:
return sql
# 使用 execute() 方法执行 SQL 查询
self.cursor.execute(sql)
# 使用 fetchall() 方法获取所有数据.
data = self.cursor.fetchall()
return data
'''
DROP TABLE IF EXISTS `people`;
CREATE TABLE `people` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL COMMENT '名字',
`sex` varchar(7) DEFAULT '' COMMENT '性别',
`job` varchar(6) DEFAULT '' COMMENT '工作',
`age` varchar(6) DEFAULT '' COMMENT '年龄',
`height` varchar(6) DEFAULT '' COMMENT '身高',
`weight` varchar(6) DEFAULT '' COMMENT '体重',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
INSERT INTO `people` VALUES ('1', '赵一', '男', '学生', '8', '120', '35');
INSERT INTO `people` VALUES ('2', '钱二', '女', '学生', '9', '111', '31');
INSERT INTO `people` VALUES ('3', '孙三', '男', '学生', '10', '123', '34');
INSERT INTO `people` VALUES ('4', '李四', '女', '学生', '11', '100', '30');
'''
db = DB('people')
# 增加
dict = {'name': '周五', 'sex': '男', 'job': '学生', 'age': '8', 'height': '121', 'weight': '32'}
data = db.insert(dict)
print(data)
# 删除
# data = db.where('id=6').delete()
# print(data)
# 修改
# dict = {'age': '9', 'height': '121', 'weight': '31'}
# data = db.where('id=7').update(dict)
# print(data)
# 查询 优化where条件 'id<11'
# data = db.field('id,name,age,job').where([['id', ' ', 1]]).order('id desc').limit('3').select()
# print(data)