可以使用psycopg2模块将PostgreSQL与Python集成. sycopg2是用于Python编程语言的PostgreSQL数据库适配器. psycopg2的写作目的是非常小而快，并且像岩石一样稳定.您不需要单独安装此模块，因为默认情况下它与Python 2.5.x版本一起发货.
如果您的计算机上没有安装它，那么您可以使用yum命令安装它如下 :
$ yum install python-psycopg2
要使用psycopg2模块，必须首先创建一个表示数据库的Connection对象，然后可以选择创建游标对象，它将帮助您执行所有SQL语句.
以下是重要的psycopg2模块例程，它们可以满足您从Python程序使用PostgreSQL数据库的要求.如果您正在寻找更复杂的应用程序，那么您可以查看Python psycopg2模块的官方文档.
| S.不. | API&描述 |
|---|---|
| 1 | psycopg2.connect(database ="testdb"，user ="postgres"，password ="cohondob"，host ="127.0.0.1"，port ="5432") 此API打开与PostgreSQL数据库的连接.如果数据库成功打开，它将返回一个连接对象. |
| 2 | connection.cursor() 这个例程创建了一个游标，它将在你的Python数据库编程中使用. |
| 3 | cursor.execute(sql [，可选]参数]) 此例程执行SQL语句.可以参数化SQL语句(即占位符而不是SQL文本). psycopg2模块支持占位符使用%s符号 例如:cursor.execute("插入人值(%s，%s)"，(谁，年龄)) |
| 4 | cursor.executemany(sql，seq_of_parameters) 此例程针对所有参数序列或映射执行SQL命令在序列sql中找到. |
| 5 | cursor.callproc(procname [，parameters]) 这个例程执行具有给定名称的存储数据库过程.参数序列必须包含过程所期望的每个参数的一个条目. |
| 6 | cursor.rowcount 此只读属性，返回上次执行*()修改，插入或删除的数据库行总数. |
| 7 | connection.commit() 此方法提交当前事务.如果不调用此方法，则自上次调用commit()以来所做的任何事情都不会从其他数据库连接中看到. |
| 8 | connection.rollback() 此方法回滚自上次调用commit()以来对数据库的任何更改. |
| 9 | connection.close() 此方法关闭数据库连接.请注意，这不会自动调用commit().如果您只是先关闭数据库连接而不先调用commit()，那么您的更改将会丢失！ |
| 10 | cursor.fetchone() 此方法获取查询结果集的下一行，返回单个序列，或者在没有更多数据可用时获取无. |
| 11 | cursor.fetchmany([size = cursor.arraysize]) 此例程获取查询结果的下一组行，返回一个列表.没有更多行可用时返回空列表.该方法尝试获取size参数指示的行数. |
| 12 | cursor.fetchall() 此例程提取查询结果的所有(剩余)行，返回一个列表.没有行可用时返回空列表. |
以下Python代码显示了如何连接到现有数据库.如果数据库不存在，那么它将被创建，最后将返回一个数据库对象.
#!/usr/bin/python import psycopg2 conn = psycopg2.connect(database="testdb", user = "postgres", password = "pass123", host = "127.0.0.1", port = "5432") print "Opened database successfully"
在这里，您还可以提供数据库 testdb 作为名称，如果数据库成功打开，那么它将给出以下消息 :
Open database successfully
以下Python程序将用于在先前创建的数据库中创建表 :
#!/usr/bin/python
import psycopg2
conn = psycopg2.connect(database = "testdb", user = "postgres", password = "pass123", host = "127.0.0.1", 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()当执行上述给定程序时，它将创建您的 test.db 中的公司表格，它将显示以下消息 :
Opened database successfully Table created successfully
以下Python程序显示了我们如何在创建的COMPANY表中创建记录在上面的示例中 :
#!/usr/bin/python
import psycopg2
conn = psycopg2.connect(database = "testdb", user = "postgres", password = "pass123", host = "127.0.0.1", 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,NAME,AGE,ADDRESS,SALARY) \
VALUES (2, 'Allen', 25, 'Texas', 15000.00 )");
cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
VALUES (3, 'Teddy', 23, 'Norway', 20000.00 )");
cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 )");
conn.commit()
print "Records created successfully";
conn.close()当执行上面给出的程序时，它将在COMPANY表中创建给定记录并显示以下两行 :
Opened database successfully Records created successfully
以下Python程序显示了我们如何从上面示例中创建的COMPANY表中获取和显示记录 :
#!/usr/bin/python
import psycopg2
conn = psycopg2.connect(database = "testdb", user = "postgres", password = "pass123", host = "127.0.0.1", 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], "\n"
print "Operation done successfully";
conn.close()当执行上面给出的程序时，它将产生以下结果 :
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
以下Python代码显示了我们如何使用UPDATE语句更新任何记录然后从我们的COMPANY表中获取并显示更新的记录 :
#!/usr/bin/python
import psycopg2
conn = psycopg2.connect(database = "testdb", user = "postgres", password = "pass123", host = "127.0.0.1", port = "5432")
print "Opened database successfully"
cur = conn.cursor()
cur.execute("UPDATE COMPANY set SALARY = 25000.00 where ID = 1")
conn.commit()
print "Total number of rows updated :", cur.rowcount
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], "\n"
print "Operation done successfully";
conn.close()当执行上面给出的程序时，它将产生以下结果 :
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
以下Python代码显示我们如何使用DELETE语句删除任何记录，然后从我们的COMPANY表中获取并显示剩余记录 :
#!/usr/bin/python
import psycopg2
conn = psycopg2.connect(database = "testdb", user = "postgres", password = "pass123", host = "127.0.0.1", port = "5432")
print "Opened database successfully"
cur = conn.cursor()
cur.execute("DELETE from COMPANY where ID=2;")
conn.commit()
print "Total number of rows deleted :", cur.rowcount
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], "\n"
print "Operation done successfully";
conn.close()当执行上面给出的程序时，它将产生以下结果 :
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
