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：https://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 

>>>