一、安装PostgreSQL模块
pip install psycopg2
有时候会失败，多安装2次就好了(我是第二次成功了)。
二、数据库连接接口
由于Python统一了数据库连接的接口，所以psycopg2和 MySQLdb 在使用方式上是类似的：
pymysql.Connect()参数说明
host(str): MySQL服务器地址
port(int): MySQL服务器端口号
user(str): 用户名
password(str): 密码
database(str): 数据库名称
connection对象支持的方法
cursor() 使用该连接创建并返回游标
commit() 提交当前事务
rollback() 回滚当前事务
close() 关闭连接
cursor对象支持的方法
execute(op) 执行一个数据库的查询命令
fetchone() 取得结果集的下一行
fetchmany(size) 获取结果集的下几行
fetchall() 获取结果集中的所有行
rowcount() 返回数据条数或影响行数
close() 关闭游标对象
三、范例
MySql脚本
-- ---------------------------- -- Table structure for account -- ---------------------------- DROP TABLE IF EXISTS `account`; CREATE TABLE `account` ( `acctid` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL, `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL, `money` decimal(50, 0) NULL DEFAULT NULL ) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; -- ---------------------------- -- Records of account -- ---------------------------- INSERT INTO `account` VALUES (‘1‘, ‘张三‘, 50); INSERT INTO `account` VALUES (‘2‘, ‘李四‘, 150);
Python程序
# coding:utf8 import sys
import psycopg2 #PostgreSQL
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
print("check_acct_available:" + sql)
cursor.execute(sql)
rs = cursor.fetchall()
if len(rs) != 1:
raise Exception("帐号%s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)
print("has_enough_money:" + sql)
cursor.execute(sql)
rs = cursor.fetchall()
if len(rs) != 1:
raise Exception("帐号%s没有足够的金额" % 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)
print("reduce_money:" + sql)
cursor.execute(sql)
if cursor.rowcount != 1:
raise Exception("帐号%s减款失败" % 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)
print("add_money:" + sql)
cursor.execute(sql)
if cursor.rowcount != 1:
raise Exception("帐号%s加款失败" % 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()
print("transfer出现异常：" + str(e))
raise e
def main():
source_acctid = sys.argv[1]
print("转出帐号=" + source_acctid)
target_acctid = sys.argv[2]
print("转入帐号=" + target_acctid)
money = sys.argv[3]
print("金额=" + money)
# 连接数据库 MySql
#conn = pymysql.Connect(
# host=‘localhost‘,
# port=3306,
# user=‘root‘,
# passwd=‘root‘,
# db=‘OtkDb‘,
# charset=‘utf8‘)
# 连接数据库PostgreSQL
conn = psycopg2.connect(
host=‘localhost‘,
port=5432,
user=‘postgres‘,
password=‘postgres‘,
database=‘OtkDb‘)
tr_money = TransferMoney(conn)
try:
tr_money.transfer(source_acctid, target_acctid, money)
except Exception as e:
print("main出现异常：" + str(e))
finally:
conn.close()
if __name__ == ‘__main__‘:
main()
四、运行效果
PS H:\web\Python> & python h:\web\Python\01.MySql\db.py 1 2 50 转出帐号=1 转入帐号=2 金额=50 check_acct_available:select * from account where acctid=‘1‘ check_acct_available:select * from account where acctid=‘2‘ has_enough_money:select * from account where acctid=‘1‘ and money>50 reduce_money:update account set money=money-50 where acctid=‘1‘ add_money:update account set money=money+50 where acctid=‘2‘
PS H:\web\Python> & python h:\web\Python\01.MySql\db.py 1 2 50 转出帐号=1 转入帐号=2 金额=50 check_acct_available:select * from account where acctid=‘1‘ check_acct_available:select * from account where acctid=‘2‘ has_enough_money:select * from account where acctid=‘1‘ and money>50 transfer出现异常：帐号1没有足够的金额 main出现异常：帐号1没有足够的金额
参考：
https://www.cnblogs.com/Erick-L/p/7106816.html
