linux python pymysql,Python之pymysql的使用
在Python3.x中，可以使用pymysql來MySQL數據庫的連接，并實現數據庫的各種操作，本次博客主要介紹了pymysql的安裝和使用方法。
PyMySQL的安裝
一、.windows上的安裝方法：
在python3.6中，自帶pip3，所以在python3中可以直接使用pip3去安裝所需的模塊：
pip3 install pymysql -i https://pypi.douban.com/simple
二、.linux下安裝方法：
1.tar包下載及解壓
下載tar包wget https://pypi.python.org/packages/29/f8/919a28976bf0557b7819fd6935bfd839118aff913407ca58346e14fa6c86/PyMySQL-0.7.11.tar.gz#md5=167f28514f4c20cbc6b1ddf831ade772
解壓并展開tar包tar xf PyMySQL-0.7.11.tar.gz
2.安裝
[root@localhost PyMySQL-0.7.11]# python36 setup.py install
數據庫的連接
本次測試創建的數據及表：
#創建數據庫及表，然后插入數據
mysql> create databasedbforpymysql;
mysql> create table userinfo(id int not null auto_increment primary key,username varchar(10),passwd varchar(10))engine=innodb default charset=utf8;
mysql> insert into userinfo(username,passwd) values('frank','123'),('rose','321'),('jeff',666);
#查看表內容
mysql> select * fromuserinfo;+----+----------+--------+
| id | username | passwd |
+----+----------+--------+
| 1 | frank | 123 |
| 2 | rose | 321 |
| 3 | jeff | 666 |
+----+----------+--------+
3 rows in set (0.00 sec)
連接數據庫：
importpymysql#連接數據庫
db = pymysql.connect("localhost","root","LBLB1212@@","dbforpymysql")#使用cursor()方法創建一個游標對象
cursor =db.cursor()#使用execute()方法執行SQL語句
cursor.execute("SELECT * FROM userinfo")#使用fetall()獲取全部數據
data =cursor.fetchall()#打印獲取到的數據
print(data)#關閉游標和數據庫的連接
cursor.close()
db.close()#運行結果
((1, 'frank', '123'), (2, 'rose', '321'), (3, 'jeff', '666'))
要完成一個MySQL數據的連接，在connect中可以接受以下參數：
def __init__(self, host=None, user=None, password="",
database=None, port=0, unix_socket=None,
charset='', sql_mode=None,
read_default_file=None, conv=None, use_unicode=None,
client_flag=0, cursorclass=Cursor, init_command=None,
connect_timeout=10, ssl=None, read_default_group=None,
compress=None, named_pipe=None, no_delay=None,
autocommit=False, db=None, passwd=None, local_infile=False,
max_allowed_packet=16*1024*1024, defer_connect=False,
auth_plugin_map={}, read_timeout=None, write_timeout=None,
bind_address=None):
參數解釋：
host: Host where the database serveris located #主機名或者主機地址
user: Username to log in as #用戶名
password: Password to use. #密碼
database: Database to use, None to not use a particular one. #指定的數據庫
port: MySQL port to use, default is usually OK. (default: 3306) #端口，默認是3306
bind_address: When the client has multiple network interfaces, specify
the interfacefromwhich to connect to the host. Argument can be
a hostnameor an IP address. #當客戶端有多個網絡接口的時候，指點連接到數據庫的接口，可以是一個主機名或者ip地址
unix_socket: Optionally, you can use a unix socket rather than TCP/IP.
charset: Charset you want to use.#指定字符編碼
sql_mode: Default SQL_MODE to use.
read_default_file:
Specifies my.cnf file to read these parametersfromunder the [client] section.
conv:
Conversion dictionary to use instead of the default one.
Thisis used to provide custom marshalling andunmarshaling of types.
See converters.
use_unicode:
Whetheror notto default to unicode strings.
This option defaults to trueforPy3k.
client_flag: Custom flags to send to MySQL. Find potential valuesinconstants.CLIENT.
cursorclass: Custom cursorclassto use.
init_command: Initial SQL statement to run when connectionisestablished.
connect_timeout: Timeout before throwing an exception when connecting.
(default:10, min: 1, max: 31536000)
ssl:
A dict of arguments similar to mysql_ssl_set()'s parameters.
For now the capath and cipher arguments are notsupported.
read_default_group: Group to readfrom inthe configuration file.
compress; Not supported
named_pipe: Not supported
autocommit: Autocommit mode. None means use server default. (default: False)
local_infile: Boolean to enable the use of LOAD DATA LOCAL command. (default: False)
max_allowed_packet: Max size of packet sent to serverinbytes. (default: 16MB)
Only used to limit size of"LOAD LOCAL INFILE"data packet smaller than default (16KB).
defer_connect: Don't explicitly connect on contruction - wait for connect call.
(default: False)
auth_plugin_map: A dict of plugin names to aclassthat processes that plugin.
Theclasswill take the Connection object as the argument to the constructor.
Theclassneeds an authenticate method taking an authentication packet as
an argument. For the dialog plugin, a prompt(echo, prompt) method can be used
(if no authenticate method) for returning a string fromthe user. (experimental)
db: Aliasfor database. (forcompatibility to MySQLdb)
passwd: Aliasfor password. (for compatibility to MySQLdb)
參數
cursor其實是調用了cursors模塊下的Cursor的類，這個模塊主要的作用就是用來和數據庫交互的，當你實例化了一個對象的時候，你就可以調用對象下面的各種綁定方法：
classCursor(object):"""This is the object you use to interact with the database."""
defclose(self):"""Closing a cursor just exhausts all remaining data."""
def setinputsizes(self, *args):"""Does nothing, required by DB API."""
def setoutputsizes(self, *args):"""Does nothing, required by DB API."""
def execute(self, query, args=None):"""Execute a query
:param str query: Query to execute.
:param args: parameters used with query. (optional)
:type args: tuple, list or dict
:return: Number of affected rows
:rtype: int
If args is a list or tuple, %s can be used as a placeholder in the query.
If args is a dict, %(name)s can be used as a placeholder in the query."""
defexecutemany(self, query, args):#type: (str, list) -> int
"""Run several data against one query
:param query: query to execute on server
:param args: Sequence of sequences or mappings. It is used as parameter.
:return: Number of rows affected, if any.
This method improves performance on multiple-row INSERT and
REPLACE. Otherwise it is equivalent to looping over args with
execute()."""
deffetchone(self):"""Fetch the next row"""
def fetchmany(self, size=None):"""Fetch several rows"""
deffetchall(self):"""Fetch all the rows"""......
一些綁定方法
數據庫操作
一、數據庫增刪改操作
commit()方法：在數據庫里增、刪、改的時候，必須要進行提交，否則插入的數據不生效。
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor=db.cursor()
sql= "INSERT INTO userinfo(username,passwd) VALUES('jack','123')"cursor.execute(sql)
db.commit()#提交數據
cursor.close()
db.close()
或者在execute提供插入的數據importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor=db.cursor()
sql= "INSERT INTO userinfo(username,passwd) VALUES(%s,%s)"cursor.execute(sql,("bob","123"))
db.commit()#提交數據
cursor.close()
db.close()
小知識點，mysql的注入問題：
在mysql中使用"--"代表注釋，比如現在來實現一個用戶登錄的小程序：
用戶名和密碼都存在表userinfo中，表內容如下：
mysql> select * fromuserinfo;+----+----------+--------+
| id | username | passwd |
+----+----------+--------+
| 1 | frank | 123 |
| 2 | rose | 321 |
| 3 | jeff | 666 |
+----+----------+--------+
3 rows in set (0.00sec)
小程序代碼如下：importpymysql
user= input("username:")
pwd= input("password:")
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor= db.cursor(cursor=pymysql.cursors.DictCursor)
sql= "select * from userinfo where username='%s' and passwd='%s'" %(user,pwd)
result=cursor.execute(sql)
cursor.close()
db.close()ifresult:print('登錄成功')else:print('登錄失敗')#正確登錄的運行結果
username:frank
password:123result:1登錄成功#錯誤登錄的運行結果
username:frank
password:1231231result: 0
登錄失敗
看起來沒有什么問題，但是試試下面的方式吧----------------------------------------------username:'or 1=1 --
password:123result:3登錄成功----------------------------------------------咦~也登錄成功了.
為什么呢？可以看一下現在的執行的sql語句：
select* from userinfo where username='' or 1=1 -- 'and passwd='123'這里--后面的會被注釋，所以where一定會成功，這里等于查看了所有行的內容，返回值也不等于0，所以就登錄成功了。
解決方法就是將變量或者實參直接寫到execute中即可：
result=cursor.execute(sql,(user,pwd))
在鍵入類似'or 1=1 -- 的時候就不會登錄成功了。
MySQL的注入問題
executemany()：用來同時插入多條數據：
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor=db.cursor()
sql= "INSERT INTO userinfo(username,passwd) VALUES(%s,%s)"cursor.executemany(sql,[("tom","123"),("alex",'321')])
db.commit()#提交數據
cursor.close()
db.close()
execute()和executemany()都會返回受影響的行數：
sql = "delete from userinfo where username=%s"res= cursor.executemany(sql,("jack",))print("res=",res)#運行結果
res= 1
當表中有自增的主鍵的時候，可以使用lastrowid來獲取最后一次自增的ID：
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor=db.cursor()
sql= "INSERT INTO userinfo(username,passwd) VALUES(%s,%s)"cursor.execute(sql,("zed","123"))print("the last rowid is",cursor.lastrowid)
db.commit()#提交數據
cursor.close()
db.close()#運行結果
the last rowid is 10
二、數據庫的查詢操作
這里主要介紹三個綁定方法：
fetchone():獲取下一行數據，第一次為首行；
fetchall():獲取所有行數據源
fetchmany(4):獲取下4行數據
先來查看表的內容：
mysql> select * fromuserinfo;+----+----------+--------+
| id | username | passwd |
+----+----------+--------+
| 1 | frank | 123 |
| 2 | rose | 321 |
| 3 | jeff | 666 |
| 5 | bob | 123 |
| 8 | jack | 123 |
| 10 | zed | 123 |
+----+----------+--------+
6 rows in set (0.00 sec)
使用fetchone()：
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor=db.cursor()
sql= "SELECT * FROM userinfo"cursor.execute(sql)
res= cursor.fetchone() #第一次執行
print(res)
res= cursor.fetchone() #第二次執行
print(res)
cursor.close()
db.close()#運行結果
(1, 'frank', '123')
(2, 'rose', '321')
使用fetchall()：
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor=db.cursor()
sql= "SELECT * FROM userinfo"cursor.execute(sql)
res= cursor.fetchall() #第一次執行
print(res)
res= cursor.fetchall() #第二次執行
print(res)
cursor.close()
db.close()#運行結果
((1, 'frank', '123'), (2, 'rose', '321'), (3, 'jeff', '666'), (5, 'bob', '123'), (8, 'jack', '123'), (10, 'zed', '123'))
()
可以看到，第二次獲取的時候，什么數據都沒有獲取到，這個類似于文件的讀取操作。
默認情況下，我們獲取到的返回值是元組，只能看到每行的數據，卻不知道每一列代表的是什么，這個時候可以使用以下方式來返回字典，每一行的數據都會生成一個字典：
cursor = db.cursor(cursor=pymysql.cursors.DictCursor) #在實例化的時候，將屬性cursor設置為pymysql.cursors.DictCursor
使用fetchall獲取所有行的數據，每一行都被生成一個字典放在列表里面：
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
cursor= db.cursor(cursor=pymysql.cursors.DictCursor)
sql= "SELECT * FROM userinfo"cursor.execute(sql)
res=cursor.fetchall()print(res)
cursor.close()
db.close()#運行結果
[{'id': 1, 'username': 'frank', 'passwd': '123'}, {'id': 2, 'username': 'rose', 'passwd': '321'}, {'id': 3, 'username': 'jeff', 'passwd': '666'}, {'id': 5, 'username': 'bob', 'passwd': '123'}, {'id': 8, 'username': 'jack', 'passwd': '123'}, {'id': 10, 'username': 'zed', 'passwd': '123'}]
這樣獲取到的內容就能夠容易被理解和使用了！
在獲取行數據的時候，可以理解開始的時候，有一個行指針指著第一行的上方，獲取一行，它就向下移動一行，所以當行指針到最后一行的時候，就不能再獲取到行的內容，所以我們可以使用如下方法來移動行指針：
cursor.scroll(1,mode='relative') #相對當前位置移動
cursor.scroll(2,mode='absolute') #相對絕對位置移動
第一個值為移動的行數，整數為向下移動，負數為向上移動，mode指定了是相對當前位置移動，還是相對于首行移動
例如：
sql = "SELECT * FROM userinfo"cursor.execute(sql)
res=cursor.fetchall()print(res)
cursor.scroll(0,mode='absolute') #相對首行移動了0，就是把行指針移動到了首行
res = cursor.fetchall() #第二次獲取到的內容
print(res)#運行結果
[{'id': 1, 'username': 'frank', 'passwd': '123'}, {'id': 2, 'username': 'rose', 'passwd': '321'}, {'id': 3, 'username': 'jeff', 'passwd': '666'}, {'id': 5, 'username': 'bob', 'passwd': '123'}, {'id': 8, 'username': 'jack', 'passwd': '123'}, {'id': 10, 'username': 'zed', 'passwd': '123'}]
[{'id': 1, 'username': 'frank', 'passwd': '123'}, {'id': 2, 'username': 'rose', 'passwd': '321'}, {'id': 3, 'username': 'jeff', 'passwd': '666'}, {'id': 5, 'username': 'bob', 'passwd': '123'}, {'id': 8, 'username': 'jack', 'passwd': '123'}, {'id': 10, 'username': 'zed', 'passwd': '123'}]
上下文管理器
在python的文件操作中支持上下文管理器，在操作數據庫的時候也可以使用：
importpymysql
config={"host":"127.0.0.1","user":"root","password":"LBLB1212@@","database":"dbforpymysql"}
db= pymysql.connect(**config)
with db.cursor(cursor=pymysql.cursors.DictCursor) as cursor: #獲取數據庫連接的對象
sql = "SELECT * FROM userinfo"cursor.execute(sql)
res=cursor.fetchone()print(res)
cursor.scroll(2,mode='relative')
res=cursor.fetchone()print(res)
cursor.close()
db.close()#運行結果
{'id': 1, 'username': 'frank', 'passwd': '123'}
{'id': 5, 'username': 'bob', 'passwd': '123'}
上下文管理器可以使代碼的可讀性更強。
總結
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