Python中用psycopg2模块操作PostgreSQL方法

2020-01-04 16:14:44

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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?

Python,psycopg2,PostgreSQL

编写上面代码，运行看是否抛出缺少psycopg2模块。

Python,psycopg2,PostgreSQL

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/

Python,psycopg2,PostgreSQL

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

Python,psycopg2,PostgreSQL

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。

Python,psycopg2,PostgreSQL

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 osimport sysimport psycopg2def 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 osimport sysimport psycopg2def 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 win32Type "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 win32Type "copyright", "credits" or "license()" for more information.>>> ========== RESTART: C:/Users/Administrator/Desktop/mutilpleTest.py ==========Total number of rows updated : 1id= 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 win32Type "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 deleteend deleteTotal number of rows deleted : 1id= 1 ,name= member0 ,pwd= password0 ,singal= signal0 id= 3 ,name= member2 ,pwd= password2 ,singal= signal2 id= 4 ,name= member3 ,pwd= password3 ,singal= signal3 >>>

Python,psycopg2,PostgreSQL