Mysql Cookbook学习笔记第二章
时间：2014-07-22 23:11:15
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1，使用python链接mysql
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# -*- coding: utf-8 -*-# connect.py --连接到MySQL服务器import
sysimport
MySQLdbtry: conn =
MySQLdb.connect(db =
"cookbook", host =
"localhost", user =
"burness", passwd =
"123456") print
"Connected"except: print
"Cannot connect to server" sys.exit(1)conn.close()print
"Disconnected" |
2，使用python操作过程中提示出错信息以便于调试
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# -*- coding: utf-8 -*-# connect.py --连接到MySQL服务器import
sysimport
MySQLdbtry: conn =
MySQLdb.connect(db =
"cookbook", host =
"localhost", user =
"burness", passwd =
"123456") print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to server" print
"Error code:", e.args[0] print
"Error message:", e.args[1] sys.exit(1)conn.close()print
"Disconnected" |
例如：使用错误的密码：
3，编写库文件
库文件可以简化在程序中频繁使用配置参数，以及保证一些数据的隐秘性如密码
例如 Cookbook.py内保存有数据库连接的内容：
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# -*- coding: utf-8 -*-# Cookbook.py -具有通过MySQLdb模块连接MySQL的工具方法的库文件import
MySQLdbhost_name="localhost"db_name="cookbook"user_name="burness"password="123456"# 建立一个到cookbook数据库的连接，返回一个connection对象# 如果不能建立连接则抛出一个异常。def
connect(): return
MySQLdb.connect(db=db_name, host=host_name, user=user_name, passwd=password) |
harness.py 测试Cookbook.py
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import
sysimport
MySQLdbimport
Cookbook# 用来测试Cookbook.pytry: conn=Cookbook.connect() print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to serve" print
"Error code:",e.args[0] print
"Error message:",e.args[1] sys.exit(1)conn.close()print
"Disconnected" |
4,发起语句并检索结果
python 中MySQLdb使用cursor来进行execute的操作,不返回结果如update:
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expand sourceview sourceprint?·········10········20········30········40········50········60········70········80········90········100·······110·······120·······130·······140·······15001.import
sys 02.import
MySQLdb 03.import
Cookbook 04.# 用来测试Cookbook.py 05.try: 06.
conn=Cookbook.connect() 07.
print "Connected"08.except
MySQLdb.Error, e: 09.
print "Cannot connect to serve"10.
print "Error code:",e.args[0] 11.
print "Error message:",e.args[1] 12.
sys.exit(1) 13.# cursor=conn.cursor() 14.# 使用行作为命名元素 15.cursor
= conn.cursor(MySQLdb.cursors.DictCursor) 16.cursor.execute("select id, name, cats from profile") 17.rows=cursor.fetchall() 18.#for row in rows: 19.# print "id：%s, name: %s, cats: %s" % (row[0],row[1],row[2]) 20.for
row in
rows: 21.
print "id：%s, name: %s, cats: %s" % (row["id"],row["name"],row["cats"]) 22.print
"Number of rows returned: %d" % cursor.rowcount 23.conn.close() 24.print
"Disconnected" |
返回结果，如select
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import
sysimport
MySQLdbimport
Cookbook# 用来测试Cookbook.pytry: conn=Cookbook.connect() print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to serve" print
"Error code:",e.args[0] print
"Error message:",e.args[1] sys.exit(1)cursor=conn.cursor()cursor.execute("select id, name, cats from profile")while
1: row=cursor.fetchone()# fetchone用来顺序返回下一行 if
row==None: break print
"id: %s, name: %s, cats: %s" %(row[0],row[1],row[2])print
"Number of rows returned: %d" % cursor.rowcountconn.close()print
"Disconnected" |
使用fetchall()可以一次返回整个满足条件的结果集
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import
sysimport
MySQLdbimport
Cookbook# 用来测试Cookbook.pytry: conn=Cookbook.connect() print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to serve" print
"Error code:",e.args[0] print
"Error message:",e.args[1] sys.exit(1)# cursor=conn.cursor()# 使用行作为命名元素cursor =
conn.cursor(MySQLdb.cursors.DictCursor)cursor.execute("select id, name, cats from profile")rows=cursor.fetchall()#for row in rows:# print "id：%s, name: %s, cats: %s" % (row[0],row[1],row[2])for
row in
rows: print
"id：%s, name: %s, cats: %s" % (row["id"],row["name"],row["cats"])print
"Number of rows returned: %d" % cursor.rowcountconn.close()print
"Disconnected" |
5,处理语句中的特殊字符和NULL值
占位符机制和引用：
python中可以使用格式化来进行占位符的使用
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import
sysimport
MySQLdbimport
Cookbook# 用来测试Cookbook.pytry: conn=Cookbook.connect() print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to serve" print
"Error code:",e.args[0] print
"Error message:",e.args[1] sys.exit(1)cursor =
conn.cursor()# 使用占位符来与mysql交互，python中支持格式化符号用来作为占位符cursor.execute("""insert into profile (name,birth,color,foods,cats)values(%s,%s,%s,%s,%s)""",("De‘Mont","1973-01-12",None,"eggroll",4))print
"Number of rows update: %d"%cursor.rowcountcursor2=conn.cursor()cursor2.execute("select * from profile")rows=cursor2.fetchall()for
row in
rows: print
"id：%s, name: %s, cats: %s" % (row[0],row[1],row[2])print
"Number of rows returned: %d" % cursor2.rowcountconn.close()print
"Disconnected" |
另外一个方法是MySQLdb引用时使用literal()方法
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import
sysimport
MySQLdbimport
Cookbook# 用来测试Cookbook.pytry: conn=Cookbook.connect() print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to serve" print
"Error code:",e.args[0] print
"Error message:",e.args[1] sys.exit(1)# cursor=conn.cursor()# 使用行作为命名元素cursor =
conn.cursor()# 使用占位符来与mysql交互，python中支持格式化符号用来作为占位符cursor.execute("""insert into profile (name,birth,color,foods,cats)values(%s,%s,%s,%s,%s)"""%(conn.literal("123123123123"),conn.literal("1973-01-12"),conn.literal("123"),conn.literal("eggroll"),conn.literal(4)))conn.commit()# 必须要有这个才能提交，才会有保存print
"Number of rows update: %d"%cursor.rowcountconn.close()print
"Disconnected" |
在实验代码的过程中发现上一个运行后在本地mysql数据库中没有保存，google之后发现必须在完成之后运行conn.commit()才能使更改保存！！！
6,识别结果集中的NULL值
python程序使用None来表示结果集中的NULL，代码如下：
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import
sysimport
MySQLdbimport
Cookbook# 用来测试Cookbook.pytry: conn=Cookbook.connect() print
"Connected"except
MySQLdb.Error, e: print
"Cannot connect to serve" print
"Error code:",e.args[0] print
"Error message:",e.args[1] sys.exit(1)# cursor=conn.cursor()# 使用行作为命名元素cursor =
conn.cursor()# 使用占位符来与mysql交互，python中支持格式化符号用来作为占位符cursor.execute("select name, birth, foods from profile")for
row in
cursor.fetchall(): row=list(row) for
i in
range(0,len(row)): if
row[i]==None: row[i]="NULL" print
"name: %s, birth: %s, food: %s"%(row[0],row[1],row[2])conn.close()print
"Disconnected" |
7,获取连接参数的技术
a,将参数硬编码到程序中；b,交互式请求参数;c，从命令行获取参数；d，从执行环境获取参数；e，从一个独立的文件中获取参数
从命令行得到参数可以通过getopt.getopt，具体代码如下：
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# -*- coding: cp936 -*-#cmdline.py -- 说明Python中的命令行选项解析import
sysimport
getoptimport
MySQLdbtry: opts, args=getopt.getopt(sys.argv[1:],"h:p:u:",["host=","password=","user="])# h: p: u: 表示后面都带参数 如是hp：则说明h不带参数 print
optsexcept
getopt.error,e: #对于错误，输出程序名以及错误信息文本 print
"%s: %s" %(sys.argv[0],e) sys.exit(1)host_name=password=user_name=""for
opt,arg in
opts: if
opt in
("-h","--host"): host_name=arg elif
opt in
("-p","--password"): password=arg elif
opt in
("-u","--user"): user_name=arg#所有剩下的非选项参数都保留在args中，并可在这里做必要的处理try: conn=MySQLdb.connect(db="cookbook",host=host_name,user=user_name,passwd=password) print
"Connected"except
MySQLdb.Error,e: print
"Cannot connect to server" print
"Error:",e.args[1] print
"Code:",e.args[0] sys.exit(1)conn.close()print
"Disconnected" |
从选项文件获取参数
Unix下有/etc/my.cnf,mysql安装目录的my.cnf,以及当前用户的~/.my.cnf（按系统查找顺序来），当存在多个时，最后发现的具有最高优先级而在windows下安装目录my.ini，windows根目录my.ini或者my.cnf
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