安装

Postgresql可以用Python psycopg2模块集成。 sycopg2是Python编程语言的Postgresql数据库的适配器。 其程序代码少，速度快，稳定。不需要单独安装这个模块，因为它默认情况下被运往随着Python版本在2.5.x一起的。如果不把它安装在机器上，然后可以使用yum命令安装它，如下所示：

$yum install python-psycopg2

要使用psycopg2的模块，首先必须创建一个Connection对象，它表示数据库然后再可以选择创建游标对象，这将帮助执行的所有sql语句。

Python psycopg2 模块APIs

以下是psycopg2的重要的的模块例程可以满足Python程序与Postgresql数据库的工作。如果寻找一个更复杂的应用程序，那么可以看看Python psycopg2的模块的官方文档。

连接到数据库

Python代码显示了如何连接到一个现有的数据库。如果数据库不存在，那么它就会被创建，最终将返回一个数据库对象。

#!/usr/bin/pythonimport psycopg2

conn = psycopg2.connect(database="testdb",password="pass123",port="5432")print "Opened database successfully"

在这里，也可以提供数据库testdb的名称，如果数据库成功打开，那么它会给下面的消息：

Open database successfully

创建表

以下Python程序将使用以前创建的数据库中创建一个表：

#!/usr/bin/pythonimport psycopg2

conn = psycopg2.connect(database="testdb",port="5432")print "Opened database successfully"cur = conn.cursor()cur.execute('''CREATE TABLE COMPANY
    (ID INT PRIMARY KEY   NOT NULL,NAME      TEXT  NOT NULL,AGE      INT   NOT NULL,ADDRESS    CHAR(50),SALARY     REAL);''')print "Table created successfully"conn.commit()conn.close()

上述程序执行时，它会创建表COMPANY 在数据库test.db中，它会显示以下消息：

Opened database successfully
Table created successfully

INSERT 操作

Python程序显示了我们如何创建表COMPANY 在上面的例子中创建表中的记录：

#!/usr/bin/pythonimport psycopg2

conn = psycopg2.connect(database="testdb",port="5432")print "Opened database successfully"cur = conn.cursor()cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) 
   VALUES (1,'Paul',32,'California',20000.00 )");cur.execute("INSERT INTO COMPANY (ID,SALARY) 
   VALUES (2,'Allen',25,'Texas',15000.00 )");cur.execute("INSERT INTO COMPANY (ID,SALARY) 
   VALUES (3,'Teddy',23,'Norway',SALARY) 
   VALUES (4,'Mark','Rich-Mond ',65000.00 )");conn.commit()print "Records created successfully";conn.close()

上述程序执行时，它会创建COMPANY表中的记录，并显示以下两行：

Opened database successfully
Records created successfully

SELECT 操作

Python程序，显示如何获取并显示COMPANY 表在上面的例子中创建的记录：

#!/usr/bin/pythonimport psycopg2

conn = psycopg2.connect(database="testdb",port="5432")print "Opened database successfully"cur = conn.cursor()cur.execute("SELECT id,name,address,salary from COMPANY")rows = cur.fetchall()for row in rows:
  print "ID = ",row[0]
  print "NAME = ",row[1]
  print "ADDRESS = ",row[2]
  print "SALARY = ",row[3],"
"print "Operation done successfully";conn.close()

当上述程序执行时，它会产生以下结果：

Opened database successfully
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  20000.0

ID =  2
NAME =  Allen
ADDRESS =  Texas
SALARY =  15000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

UPDATE 操作

Python代码显示如何，我们可以使用UPDATE语句来更新记录，然后从COMPANY表获取并显示更新的记录：

#!/usr/bin/pythonimport psycopg2

conn = psycopg2.connect(database="testdb",port="5432")print "Opened database successfully"cur = conn.cursor()cur.execute("UPDATE COMPANY set SALARY = 25000.00 where ID=1")conn.commitprint "Total number of rows updated :",cur.rowcount

cur.execute("SELECT id,"
"print "Operation done successfully";conn.close()

当上述程序执行时，它会产生以下结果：

Opened database successfully
Total number of rows updated : 1
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  25000.0

ID =  2
NAME =  Allen
ADDRESS =  Texas
SALARY =  15000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully

DELETE 操作

Python代码显示了如何我们可以使用DELETE语句删除记录，然后获取并显示COMPANY表剩余的记录：

#!/usr/bin/pythonimport psycopg2

conn = psycopg2.connect(database="testdb",port="5432")print "Opened database successfully"cur = conn.cursor()cur.execute("DELETE from COMPANY where ID=2;")conn.commitprint "Total number of rows deleted :","
"print "Operation done successfully";conn.close()

当上述程序执行时，它会产生以下结果：

Opened database successfully
Total number of rows deleted : 1
ID =  1
NAME =  Paul
ADDRESS =  California
SALARY =  20000.0

ID =  3
NAME =  Teddy
ADDRESS =  Norway
SALARY =  20000.0

ID =  4
NAME =  Mark
ADDRESS =  Rich-Mond
SALARY =  65000.0

Operation done successfully