Python中用psycopg2模塊操作PostgreSQL方法

更新時間：2017年11月28日 09:35:00 投稿：laozhang

python可以操作多種數(shù)據(jù)庫，本篇文章給大家介紹了用psycopg2模塊操作PostgreSQL方法，一起來學(xué)習(xí)下。

其實(shí)在Python中可以用來連接PostgreSQL的模塊很多，這里比較推薦psycopg2。psycopg2安裝起來非常的簡單（pip install psycopg2），這里主要重點(diǎn)介紹下如何使用。

安裝psycopg2模塊：

怎么驗(yàn)證是否已經(jīng)安裝過psycopy2?

編寫上面代碼，運(yùn)行看是否拋出缺少psycopg2模塊。

安裝方法1：

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

直接運(yùn)行exe，不出錯誤，運(yùn)行上邊代碼驗(yàn)證代碼無錯誤，基本算是安裝完成了。

2)怎么卸載？

2.1）找到安裝目錄：C:\Python27，發(fā)現(xiàn)下邊包含文件:Removepsycopg2.exe,運(yùn)行，來刪除；

2.2）如果運(yùn)行失敗的話，進(jìn)入目錄：C:\Python27\Lib\site-packages下，找到psycopg2文件夾和psycopg2-2.4.2-py2.7.egg-info文件，右鍵刪除。

2.3）運(yùn)行上邊的代碼，確認(rèn)是否刪除成功。

安裝方法2：

使用.whl安裝，下載地址：https://pypi.python.org/pypi/psycopg2/

下載文件：psycopg2-2.6.2-cp27-none-win_amd64.whl

我這里把psycopg2-2.6.2-cp27-none-win_amd64.whl拷貝到安裝目錄下Scripts文件夾中。

cmd中運(yùn)行代碼：pip install C:\Python27\Scripts\psycopg2-2.6.2-cp27-none-win_amd64.whl

運(yùn)行上邊的代碼，確認(rèn)是否刪除成功。

通過psycopg2操作數(shù)據(jù)庫：

使用賬戶postgres，創(chuàng)建測試數(shù)據(jù)庫testdb。

參考yiibai.comAPI:

S.N. API & 描述

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

這個API打開一個連接到PostgreSQL數(shù)據(jù)庫。如果成功打開數(shù)據(jù)庫時，它返回一個連接對象。

2 connection.cursor()

該程序創(chuàng)建一個光標(biāo)將用于整個數(shù)據(jù)庫使用Python編程。

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

此例程執(zhí)行SQL語句?？杀粎?shù)化的SQL語句（即占位符，而不是SQL文字）。 psycopg2的模塊支持占位符用％s標(biāo)志

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

4 curosr.executemany(sql, seq_of_parameters)

該程序執(zhí)行SQL命令對所有參數(shù)序列或序列中的sql映射。

5 curosr.callproc(procname[, parameters])

這個程序執(zhí)行的存儲數(shù)據(jù)庫程序給定的名稱。該程序預(yù)計(jì)為每一個參數(shù)，參數(shù)的順序必須包含一個條目。

6 cursor.rowcount

這個只讀屬性，它返回?cái)?shù)據(jù)庫中的行的總數(shù)已修改，插入或刪除最后 execute*().

7 connection.commit()

此方法提交當(dāng)前事務(wù)。如果不調(diào)用這個方法，無論做了什么修改，自從上次調(diào)用commit()是不可見的，從其他的數(shù)據(jù)庫連接。

8 connection.rollback()

此方法會回滾任何更改數(shù)據(jù)庫自上次調(diào)用commit（）方法。

9 connection.close()

此方法關(guān)閉數(shù)據(jù)庫連接。請注意，這并不自動調(diào)用commit（）。如果你只是關(guān)閉數(shù)據(jù)庫連接而不調(diào)用commit（）方法首先，那么所有更改將會丟失！

10 cursor.fetchone()

這種方法提取的查詢結(jié)果集的下一行，返回一個序列，或者無當(dāng)沒有更多的數(shù)據(jù)是可用的。

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

這個例程中取出下一個組的查詢結(jié)果的行數(shù)，返回一個列表。當(dāng)沒有找到記錄，返回空列表。該方法試圖獲取盡可能多的行所顯示的大小參數(shù)。

12 cursor.fetchall()

這個例程獲取所有查詢結(jié)果（剩余）行，返回一個列表?？招袝r則返回空列表。

打開數(shù)據(jù)庫連接：

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()

創(chuàng)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()

結(jié)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()

結(jié)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()

結(jié)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 

>>>