python操作数据库

• 连接数据库及基本操作

# 1. 连接数据库，
conn = pymysql.connect(
    host='localhost',
    user='root',
    password='redhat',
    db='helloTest', #数据库
    charset='utf8',
    # autocommit=True,    # 如果插入数据，， 是否自动提交? 和conn.commit()功能一致。
)



# 必须有一个游标对象， 用来给数据库发送sql语句， 并执行的.
# 2. 创建游标对象，
cur = conn.cursor()



# 3. 对于数据库进行增删改查
#1). ************************创建数据表**********************************
try:
    create_sqli = "create table hello (id int, name varchar(30));"
    cur.execute(create_sqli)
except Exception as e:
    print("创建数据表失败:", e)
else:
    print("创建数据表成功;")

#2). *********************插入数据****************************
try:
    insert_sqli = "insert into hello values(2, 'fensi');"
    cur.execute(insert_sqli)
except Exception as e:
    print("插入数据失败:", e)
else:
    # 如果是插入数据， 一定要提交数据， 不然数据库中找不到要插入的数据;
    conn.commit()
    print("插入数据成功;")

#3). *********************插入多条数据****************************
try:
    info = [(i, "westos%s" %(i)) for i in range(10)]
    # *********************第一种方式********************
    # # %s必须手动添加一个字符串， 否则就是一个变量名， 会报错.
    # insert_sqli = "insert into hello values(%d, '%s');"
    # for item in info:
    #     print('insert语句:', insert_sqli %item)
    #     cur.execute(insert_sqli %item)
    # *********************第二种方式********************
    insert_sqli = "insert into hello values(%s, %s);"
    cur.executemany(insert_sqli, info )
except Exception as e:
    print("插入多条数据失败:", e)
else:
    # 如果是插入数据， 一定要提交数据， 不然数据库中找不到要插入的数据;
    conn.commit()
    print("插入多条数据成功;")

# 4). **************************数据库查询*****************************
sqli = "select * from hello;"
result = cur.execute(sqli)  # 默认不返回查询结果集， 返回数据记录数。
print(result)
print(cur.fetchone())     # 1). 获取下一个查询结果集;
print(cur.fetchone())
print(cur.fetchone())

print(cur.fetchmany(4))   # 2). 获取制定个数个查询结果集；

info = cur.fetchall()     # 3). 获取所有的查询结果
print(info)
print(len(info))

print(cur.rowcount)       # 4). 返回执行sql语句影响的行数

#  5). 移动游标指针
print(cur.fetchmany(3))
print("正在移动指针到最开始......")
cur.scroll(0, 'absolute')
print(cur.fetchmany(3))

print("正在移动指针到倒数第2个......")
print(cur.fetchall())    # 移动到最后
cur.scroll(-2, mode='relative')

print(cur.fetchall())


# 4. 关闭游标
cur.close()


# 5. 关闭连接

• 获取表的字段名和信息

# 1. 连接数据库，
conn = pymysql.connect(
    host='localhost',
    user='root',
    password='redhat',
    db='helloTest',
    charset='utf8',
    # autocommit=True,
)

# with语句实现的效果是: with语句执行结束， 如果成功， 则提交改变的数据， 如果不成功， 则回滚.
with conn:
    # ****** 判断是否连接?
    print(conn.open)  # True
    # 2. 创建游标对象，
    cur = conn.cursor()
    # 3).
    sqli = "select * from hello;"
    result = cur.execute(sqli) 

    # 显示每列的详细信息
    des = cur.description
    print("表的描述:", des)

    # 获取表头
    print("表头:", ",".join([item[0] for item in des]))
    cur.close()


conn.close()
print("with语句之外:", conn.open)   # False

• 小例子
  基于mysql数据库实现银行转账功能

"""
银行账户表:
    银行卡号:
    金额:
"""
import pymysql

class TransferMoney(object):
    # 构造方法
    def __init__(self, conn):
        self.conn = conn
        self.cur = conn.cursor()

    def transfer(self, source_id, target_id, money):
        # 1). 判断两个银行卡号是否存在?
        # 2). 判断source_id是否有足够的钱？
        # 3). source_id扣钱
        # 4). target_id加钱
        if not self.check_account_avaialbe(source_id):
            raise  Exception("账户不存在")
        if not self.check_account_avaialbe(target_id):
            raise  Exception("账户不存在")

        if self.has_enough_money(source_id, money):
            try:
                self.reduce_money(source_id, money)
                self.add_money(target_id, money)
            except Exception as e:
                print("转账失败:", e)
                self.conn.rollback()
            else:
                self.conn.commit()
                print("%s给%s转账%s金额成功" % (source_id, target_id, money))

    def check_account_avaialbe(self, acc_id):
        """判断帐号是否存在， 传递的参数是银行卡号的id"""
        select_sqli = "select * from bankData where id=%d;" % (acc_id)
        print("execute sql:", select_sqli)
        res_count = self.cur.execute(select_sqli)
        if res_count == 1:
            return True
        else:
            # raise  Exception("账户%s不存在" %(acc_id))
            return False

    def has_enough_money(self, acc_id, money):
        """判断acc_id账户上金额> money"""
        # 查找acc_id存储金额?
        select_sqli = "select money from bankData where id=%d;" % (acc_id)
        print("execute sql:", select_sqli)
        self.cur.execute(select_sqli)  # ((1, 500), )

        # 获取查询到的金额钱数;
        acc_money = self.cur.fetchone()[0]
        # 判断
        if acc_money >= money:
            return True
        else:
            return False

    def add_money(self, acc_id, money):
        update_sqli = "update bankData set money=money+%d  where id=%d" % (money, acc_id)
        print("add money:", update_sqli)
        self.cur.execute(update_sqli)

    def reduce_money(self, acc_id, money):
        update_sqli = "update bankData set money=money-%d  where id=%d" % (money, acc_id)
        print("reduce money:", update_sqli)
        self.cur.execute(update_sqli)

    # 析构方法
    def __del__(self):
        self.cur.close()
        self.conn.close()


if __name__ == '__main__':
    # 1. 连接数据库，
    conn = pymysql.connect(
        host='localhost',
        user='root',
        password='redhat',
        db='helloTest',
        charset='utf8',
        autocommit=True,    # 如果插入数据，， 是否自动提交? 和conn.commit()功能一致。
    )
    trans = TransferMoney(conn)
    # 下面是测试每个方法，写一个方法就测试，最后不会报很多错
    # assert trans.check_account_avaialbe(14255632) == False
    # assert  trans.check_account_avaialbe(13997) == True
    #
    #
    # assert  trans.has_enough_money(13997, 800) == False
    # assert  trans.has_enough_money(13998, 700) == True
    # trans.add_money(13998, 200)
    # trans.reduce_money(13998, 200)
    # # trans.transfer(12567, 16787, 100)
    # trans.transfer(13997, 13998, 200)

python2操作

几乎和python3一样
yum install MySQL-python.x86_64 -y

import random
import MySQLdb as pymysql

# 1. 连接数据库
conn = pymysql.connect(
    host='localhost',
    user='root',
    passwd='redhat',
    db='helloTest',
    autocommit=True,
    charset='utf8'
)
# 2. 创建游标
cur = conn.cursor()

# create_db = "create database westos;"
# cur.execute(create_db)
# conn.select_db('westos')  # 连接数据库
# 3. 操作
bank_id = random.randint(10000, 20000)
print("创建银行账户%s ............" % (bank_id))
bank_pwd = raw_input("请输入用户密码:")
bank_money = float(raw_input("存储金额:"))
insert_sqli = "insert into bankData values(%d, %f , '%s')" % (bank_id, 0, bank_pwd)
cur.execute(insert_sqli)
print("创建账户成功........")
# 4. 关闭游标
cur.close()
# 5. 关闭连接
conn.close()