python3 的 mysql 簡單操作
阿新 • • 發佈:2017-10-13
操作 into 出現問題 ava 連接 targe exec obj 事務
一、python 提供的 db 接口
pymysql
兩個基本對象: connection、cursor
連接示例
# connect_demo.py import pymysql db = pymysql.connect(‘localhost‘, ‘root‘, ‘root‘, ‘imooc‘, charset=‘utf8‘) cursor = db.cursor() print(db) print(cursor) cursor.close() db.close()
輸出
<pymysql.connections.Connection object at 0x7f1e2a852278> <pymysql.cursors.Cursor object at 0x7f1e2880e668>
操作遊標
# cursor_demo.py import pymysql db = pymysql.connect(‘localhost‘, ‘root‘, ‘root‘, ‘imooc‘, charset=‘utf8‘) cursor = db.cursor() sql = ‘select * from user‘ cursor.execute(sql) print(cursor.rowcount) result = cursor.fetchall() print(result) for row in result: print(row[0],‘:‘, row[1]) cursor.close() db.close()
輸出
((1, ‘lisi‘), (2, ‘zhangsan‘), (3, ‘liuqi‘), (4, ‘white‘)) 1 : lisi 2 : zhangsan 3 : liuqi 4 : white
二、增刪改查
# curd_demo.py import pymysql db = pymysql.connect(‘localhost‘, ‘root‘, ‘root‘, ‘imooc‘, charset=‘utf8‘) cursor = db.cursor() sql_select = "select * from user" sql_insert = "insert into user(userid, username) values(DEFAULT, ‘wuliu‘)" sql_update = "update user set username=‘liuqi‘ where userid=3" sql_delete = "delete from user where userid>4" cursor.execute(sql_select) result = cursor.fetchall() print(result) try: cursor.execute(sql_insert) result = cursor.rowcount print(result) cursor.execute(sql_update) result = cursor.rowcount print(result) cursor.execute(sql_delete) result = cursor.rowcount print(result) db.commit() except Exception as e: print(e) db.rollback() cursor.close() db.close()
輸出
((1, ‘lisi‘), (2, ‘zhangsan‘), (3, ‘liuqi‘), (4, ‘white‘)) 1 0 1
三、事務的小示例
# bank_demo.py # coding:utf8 import sys import pymysql class TransferMoney(object): def __init__(self, conn): self.conn = conn def check_acct_available(self, acctid): cursor = self.conn.cursor() try: sql = "select * from account where acctid=%s" % acctid cursor.execute(sql) print("check_acct_available:" + sql) rs = cursor.fetchall() if len(rs) != 1: raise Exception("賬號不存在" % acctid) finally: cursor.close() def has_enough_money(self, acctid, money): cursor = self.conn.cursor() try: sql = "select * from account where acctid=%s and money>%s" % (acctid, money) cursor.execute(sql) print("chas_enough_mone:" + sql) rs = cursor.fetchall() if len(rs) != 1: raise Exception("賬號%s余額不足" % acctid) finally: cursor.close() def reduce_money(self, acctid, money): cursor = self.conn.cursor() try: sql = "update account set money=money - %s where acctid=%s" % (money, acctid) cursor.execute(sql) print("reduce_money:" + sql) if cursor.rowcount != 1: raise Exception("賬號%s減款失敗" % acctid) finally: cursor.close() def add_money(self, acctid, money): cursor = self.conn.cursor() try: sql = "update account set money=money + %s where acctid=%s" % (money, acctid) cursor.execute(sql) print("rad_money:" + sql) if cursor.rowcount != 1: raise Exception("賬號%s加款失敗" % acctid) finally: cursor.close() def transfer(self, source_acctid, target_acctid, money): try: self.check_acct_available(source_acctid) self.check_acct_available(target_acctid) self.has_enough_money(source_acctid, money) self.reduce_money(source_acctid, money) self.add_money(target_acctid, money) self.conn.commit() except Exception as e: self.conn.rollback() raise e if __name__ == "__main__": source_acctid= sys.argv[1] target_acctid= sys.argv[2] money = sys.argv[3] conn = pymysql.connect(‘localhost‘, ‘root‘, ‘root‘, ‘imooc‘, charset=‘utf8‘) tr_money = TransferMoney(conn) try: tr_money.transfer(source_acctid, target_acctid, money) except Exception as e: print("出現問題:", str(e)) finally: conn.close()
命令行運行
python bank_demo.py 3 1 1000
輸出
check_acct_available:select * from account where acctid=3 check_acct_available:select * from account where acctid=1 chas_enough_mone:select * from account where acctid=3 and money>1000 reduce_money:update account set money=money - 1000 where acctid=3 rad_money:update account set money=money + 1000 where acctid=1
python3 的 mysql 簡單操作