Python中用psycopg2模块操作PostgreSQL方法


            其实在Python中可以用来连接PostgreSQL的模块很多，这里比较推荐psycopg2。psycopg2安装起来非常的简单（pip install psycopg2），这里主要重点介绍下如何使用。

安装psycopg2模块：

怎么验证是否已经安装过psycopy2?



编写上面代码，运行看是否抛出缺少psycopg2模块。



安装方法1：



1)使用psycopg2-2.4.2.win-amd64-py2.7-pg9.0.4-release.exe安装，下载地址:http://vdisk.weibo.com/s/Cd8pPaw56Ozys

直接运行exe，不出错误，运行上边代码验证代码无错误，基本算是安装完成了。

2)怎么卸载？

2.1）找到安装目录：C:\Python27，发现下边包含文件:Removepsycopg2.exe,运行，来删除；

2.2）如果运行失败的话，进入目录：C:\Python27\Lib\site-packages下，找到psycopg2文件夹和psycopg2-2.4.2-py2.7.egg-info文件，右键删除。

2.3）运行上边的代码，确认是否删除成功。

安装方法2：



使用.whl安装，下载地址：http://pypi.python.org/pypi/psycopg2/



下载文件：psycopg2-2.6.2-cp27-none-win_amd64.whl

我这里把psycopg2-2.6.2-cp27-none-win_amd64.whl拷贝到安装目录下Scripts文件夹中。

cmd中运行代码：pip install C:\Python27\Scripts\psycopg2-2.6.2-cp27-none-win_amd64.whl



运行上边的代码，确认是否删除成功。

通过psycopg2操作数据库：



使用账户postgres，创建测试数据库testdb。



参考yiibai.comAPI:

S.N. API & 描述



1 psycopg2.connect(database="testdb", user="postgres", password="cohondob", host="127.0.0.1", port="5432") 



这个API打开一个连接到PostgreSQL数据库。如果成功打开数据库时，它返回一个连接对象。 



2 connection.cursor()



该程序创建一个光标将用于整个数据库使用Python编程。 



3 cursor.execute(sql [, optional parameters])



此例程执行SQL语句。可被参数化的SQL语句（即占位符，而不是SQL文字）。 psycopg2的模块支持占位符用％s标志 



例如：cursor.execute("insert into people values (%s, %s)", (who, age))



4 curosr.executemany(sql, seq_of_parameters)



该程序执行SQL命令对所有参数序列或序列中的sql映射。 



5 curosr.callproc(procname[, parameters])



这个程序执行的存储数据库程序给定的名称。该程序预计为每一个参数，参数的顺序必须包含一个条目。



6 cursor.rowcount



这个只读属性，它返回数据库中的行的总数已修改，插入或删除最后 execute*().



7 connection.commit()



此方法提交当前事务。如果不调用这个方法，无论做了什么修改，自从上次调用commit()是不可见的，从其他的数据库连接。



8 connection.rollback()



此方法会回滚任何更改数据库自上次调用commit（）方法。



9 connection.close()



此方法关闭数据库连接。请注意，这并不自动调用commit（）。如果你只是关闭数据库连接而不调用commit（）方法首先，那么所有更改将会丢失！ 



10 cursor.fetchone()



这种方法提取的查询结果集的下一行，返回一个序列，或者无当没有更多的数据是可用的。



11 cursor.fetchmany([size=cursor.arraysize])



这个例程中取出下一个组的查询结果的行数，返回一个列表。当没有找到记录，返回空列表。该方法试图获取尽可能多的行所显示的大小参数。



12 cursor.fetchall()



这个例程获取所有查询结果（剩余）行，返回一个列表。空行时则返回空列表。

打开数据库连接：





import os

import sys

import psycopg2

def connectPostgreSQL():

conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

print 'connect successful!'

if __name__=='__main__':

connectPostgreSQL()



创建表操作：





import os

import sys

import psycopg2

def connectPostgreSQL():

conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

print 'connect successful!'

cursor=conn.cursor()

cursor.execute('''create table public.member(

id integer not null primary key,

name varchar(32) not null,

password varchar(32) not null,

singal varchar(128)

)''')

conn.commit()

conn.close()

print 'table public.member is created!'

if __name__=='__main__':

connectPostgreSQL()



Insert 操作：





import os

 import sys

 import psycopg2

 

 def connectPostgreSQL():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   print 'connect successful!'

   cursor=conn.cursor()

   cursor.execute('''create table public.member(

 id integer not null primary key,

 name varchar(32) not null,

 password varchar(32) not null,

 singal varchar(128)

 )''')

   conn.commit()

   conn.close()

   print 'table public.member is created!'

 def insertOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(1,'member0','password0','signal0')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(2,'member1','password1','signal1')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(3,'member2','password2','signal2')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(4,'member3','password3','signal3')")

   conn.commit()

   conn.close()

   

   print 'insert records into public.memmber successfully'

   

 if __name__=='__main__':

   #connectPostgreSQL()

insertOperate()



Select 操作：





import os

 import sys

 import psycopg2

 

 def connectPostgreSQL():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   print 'connect successful!'

   cursor=conn.cursor()

   cursor.execute('''create table public.member(

 id integer not null primary key,

 name varchar(32) not null,

 password varchar(32) not null,

 singal varchar(128)

 )''')

   conn.commit()

   conn.close()

   print 'table public.member is created!'

 

 def insertOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(1,'member0','password0','signal0')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(2,'member1','password1','signal1')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(3,'member2','password2','signal2')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(4,'member3','password3','signal3')")

   conn.commit()

   conn.close()

   

   print 'insert records into public.memmber successfully'

 

 def selectOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("select id,name,password,singal from public.member where id>2")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

   conn.close()

   

 if __name__=='__main__':

   #connectPostgreSQL()

   #insertOperate()

   selectOperate()



结果：





Python 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:24:40) [MSC v.1500 64 bit (AMD64)] on win32

Type "copyright", "credits" or "license()" for more information.

>>> 

========== RESTART: C:\Users\Administrator\Desktop\mutilpleTest.py ==========

id= 3 ,name= member2 ,pwd= password2 ,singal= signal2 



id= 4 ,name= member3 ,pwd= password3 ,singal= signal3 



>>> 



update操作：





 import os

 import sys

 import psycopg2

 

 def connectPostgreSQL():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   print 'connect successful!'

   cursor=conn.cursor()

   cursor.execute('''create table public.member(

 id integer not null primary key,

 name varchar(32) not null,

 password varchar(32) not null,

 singal varchar(128)

 )''')

   conn.commit()

   conn.close()

   print 'table public.member is created!'

 

 def insertOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(1,'member0','password0','signal0')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(2,'member1','password1','signal1')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(3,'member2','password2','signal2')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(4,'member3','password3','signal3')")

   conn.commit()

   conn.close()

   

   print 'insert records into public.memmber successfully'

 

 def selectOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("select id,name,password,singal from public.member where id>2")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

   conn.close()

 

 def updateOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("update public.member set name='update ...' where id=2")

   conn.commit()

   print "Total number of rows updated :", cursor.rowcount

 

   cursor.execute("select id,name,password,singal from public.member")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

   conn.close()

   

 if __name__=='__main__':

   #connectPostgreSQL()

   #insertOperate()

   #selectOperate()

   updateOperate()



结果：





Python 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:24:40) [MSC v.1500 64 bit (AMD64)] on win32

Type "copyright", "credits" or "license()" for more information.

>>> 

========== RESTART: C:\Users\Administrator\Desktop\mutilpleTest.py ==========

Total number of rows updated : 1

id= 1 ,name= member0 ,pwd= password0 ,singal= signal0 



id= 3 ,name= member2 ,pwd= password2 ,singal= signal2 



id= 4 ,name= member3 ,pwd= password3 ,singal= signal3 



id= 2 ,name= update ... ,pwd= password1 ,singal= signal1 



>>> 



Delete操作：





 import os

 import sys

 import psycopg2

 

 def connectPostgreSQL():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   print 'connect successful!'

   cursor=conn.cursor()

   cursor.execute('''create table public.member(

 id integer not null primary key,

 name varchar(32) not null,

 password varchar(32) not null,

 singal varchar(128)

 )''')

   conn.commit()

   conn.close()

   print 'table public.member is created!'

 

 def insertOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(1,'member0','password0','signal0')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(2,'member1','password1','signal1')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(3,'member2','password2','signal2')")

   cursor.execute("insert into public.member(id,name,password,singal)\

 values(4,'member3','password3','signal3')")

   conn.commit()

   conn.close()

   

   print 'insert records into public.memmber successfully'

 

 def selectOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("select id,name,password,singal from public.member where id>2")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

   conn.close()

 

 def updateOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")

   cursor=conn.cursor()

   cursor.execute("update public.member set name='update ...' where id=2")

   conn.commit()

   print "Total number of rows updated :", cursor.rowcount

 

   cursor.execute("select id,name,password,singal from public.member")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

   conn.close()

 

 def deleteOperate():

   conn = psycopg2.connect(database="testdb", user="postgres", password="new.1234", host="127.0.0.1", port="5432")  

   cursor=conn.cursor()

 

   cursor.execute("select id,name,password,singal from public.member")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

 

   print 'begin delete'

   cursor.execute("delete from public.member where id=2")

   conn.commit()  

   print 'end delete'

   print "Total number of rows deleted :", cursor.rowcount

   

   cursor.execute("select id,name,password,singal from public.member")

   rows=cursor.fetchall()

   for row in rows:

     print 'id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n'

   conn.close()

   

 if __name__=='__main__':

   #connectPostgreSQL()

   #insertOperate()

   #selectOperate()

   #updateOperate()

   deleteOperate()



结果：





Python 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:24:40) [MSC v.1500 64 bit (AMD64)] on win32

Type "copyright", "credits" or "license()" for more information.

>>> 

========== RESTART: C:\Users\Administrator\Desktop\mutilpleTest.py ==========

id= 1 ,name= member0 ,pwd= password0 ,singal= signal0 



id= 3 ,name= member2 ,pwd= password2 ,singal= signal2 



id= 4 ,name= member3 ,pwd= password3 ,singal= signal3 



id= 2 ,name= update ... ,pwd= password1 ,singal= signal1 



begin delete

end delete

Total number of rows deleted : 1

id= 1 ,name= member0 ,pwd= password0 ,singal= signal0 



id= 3 ,name= member2 ,pwd= password2 ,singal= signal2 



id= 4 ,name= member3 ,pwd= password3 ,singal= signal3 



>>>