python学习笔记------数据库基本操作

数据库

数据库的连接

python2中：MySQLdb模块
python3中：pymysql模块

# 首先，导入pymysql
import pymysql

# 连接数据库
conn = pymysql.connect(host='localhost',user='root',passwd='redhat',db='westos',charset='utf8')

# 创建游标，给数据库发送sql指令
cur = conn.cursor()

# 执行sql语句
try:
    insert_sqli = 'insert into aa values('%s','%s')' %('user23','123') # aa为表的名字
    cur.execute(insert_sqli)
except Exception as e:
    print ('sql excute failed:%s' %(insert_sqli))
else:
    print ('sql excute success:%s' %(insert_sqli))

# 提交sql语句，作用于数据库
conn.commit()

# 先关闭游标
cur.close()

# 关闭数据库连接
conn,close()

批量插入多条数据

import pymysql

def create_user_data(n):
    users = []
    for i in range(n):
        username = 'user' + str(i+1)
        users.append(username,'000000')
    return users

# 1.数据库的连接
conn = pymysql.connect(host='localhost',user='root',passwd='redhat',db='westos',charset='utf8')

# 2.创建游标，给数据库发送sql指令
cur = conn.cursor()

# 3.执行sql语句：插入多条数据
try:
    # 执行的插入语句；
    insert_sqli = 'insert into userinfo values(%s,%s)'
    # 执行函数，随即生成n条用户数据；列表里面嵌套元组；[（'user1','000000'）,('user2','000000')]
    users = create_user_data(90)
    # 'insert into userinfo values(%s,%s)' %('user1','000000')
    cur.executemany(insert_sqli,users)

except Exception as e:
    print ('sql execute failed')
else:
    print ('sql execute success')

# 4.提交sql语句，作用以数据库
conn.commit()

# 5.先关闭游标
cur.close()

# 6.关闭数据库的连接
conn.close()

查看数据库表的内容

import pymysql

# 1.连接数据库
conn = pymysql.connect(host='localhost',user='root',passwd='redhat',db='westos',charset='utf8')

# 2.创建游标，给数据库发送sql指令
cur = conn.cursor()

# 3.执行sql语句：查看数据
res = cur.execute('select * from userinfo;')

# 每一次查看表中的一条数据
print (cur.fetchone())

# 如何移动游标；relative：相对的，相对当前游标向前还是向后移动；
# absolute，默认移动到最开始；
cur.scroll(2,'relative')
print(cur.fetchone())
cur.scroll(5,'absolute')
print(cur.fetchone())

# 查看指定条表的内容，元组里面嵌套元组；
print(cur.fetchmany(5))

# 显示所有数据
print(cur.fetchall())

# 依次将数据保存到文件中；
try:
    with open('/tmp/users.txt','w') as f:
        for userinfo in cur.fetchall():
            info = ':'.join(userinfo)
            f.write(info+'\n')
except Exception as e:
    print(e)
else:
    print('success')

# 4.先关闭游标
cur.close()

# 5.关闭数据库连接
conn.close()

封装数据库

import pymysql

db_config = {'host':'localhost','user':'root','pqsswd':'redhat','db':'westos','charset':'utf8'}

class Mysql(object):
    def __init__(self,db_config):
        try:
            self.db_config = db_config
            self.conn = pymysql.connect(**self.db_config)
            self.sur = self.conn.cursor()
        except Exception as e:
            print('连接数据库失败：', e)
        else:
            print ('连接数据库成功！')

    def __str__(self):
        return "Connect(%s user=%s db=%s)" %(self.db_config['host'],self.db_config['user'],self.db_config['db'])

    def __del__(self):
        self.conn.commit()
        self.cur.close()
        self.conn,close()

test_sql = Mysql(db_config)
print (str(test_sql))

获取单个表的字段名和信息

import pymysql

conn = pymysql.connect(host='localhost',user='root',passwd='redhat',db='westos',charset='utf8')

cur = conn.cursor()

res = cur.execute('select * from userinfo;')
desc = cur.description
print('表的描述信息：',desc)

table_header = [item[0] for item in desc]
print ('表头：',table_header)

print ('\t',join(table_header))
for row in cur.fetchall():
    print('\t'.join(row))

cur.close()    

conn.close()

使用with安全上下文管理器

import pymysql

conn = pymysql.connect(host='localhost',user='root',passwd='redhat',db='westos',charset='utf8')

with conn:
    cur = conn.cursor()

多台mysql主机的远程备份

import os
import time

mysql_list = [{'host':'172.25.254.250','user':'root','passwd':'redhat','db':'users'}]

BACKUP_DIR = '/opt/BACKUP/'

if not os.path.exists(BACKUP_DIR):
    os.mkdir(BACKUP_DIR)
    print('%s craete success!' %(BACKUP_DIR))
else:
    try:
        for host in mysql_list:
            shell_sen = 'mysqldump -h %s -u%s -p%s %s>%s'
            host_ip = host['host']
            user = host['user']
            passwd = host['passwd']
            db = hsot['db']
            backup_filename = BACKUP_DIR + '%s_%s.dump' %(host_ip,db)
            print(backup_filename)
            print(shell_sen %(host_ip,user,passwd,db,backup_filename))
            os.system(shell_sen %(host_ip,user,passwd,db,backup_filename))
            print('backup %s host' %(host_ip))
        except Exception as e:
            print (e)
        else:
            print ('success')

os.mknod(time.ctime())

# os.mknod() 方法用于创建一个指定文件名的文件系统节点（文件，设备特别文件或者命名pipe）。

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