PostgreSQL可以使用psycopg2模块与Python集成。sycopg2是一个用于Python编程语言的PostgreSQL数据库适配器。psycopg2的写作目的是非常小，速度快，稳定的磐石。您不需要单独安装此模块，因为默认情况下，它是与Python2.5.x版一起提供的。
如果您的机器上没有安装它，那么您可以使用 yum 命令按照以下方式安装它
$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，这将有助于执行所有 SQL 语句。
以下是重要的psycopg2 模块，可以满足您使用Python程序中的PostgreSQL数据库的需求。如果您正在寻找更复杂的应用程序，那么可以查看Python psycopg2模块的官方文档。
| S. No. | API & 描述 |
|---|---|
| 1 | psycopg2.connect(database="testdb", user="postgres", password="cohondob", host="127.0.0.1", port="5432") 这个 API 打开一个到 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() 创建一个游标，这个游标将在使用 Python 进行数据库编程的过程中使用。 |
| 3 | cursor.execute(sql [, optional 参数]) 执行SQL语句。SQL语句可以参数化（即占位符而不是SQL文本）。psycopg2模块支持使用%s符号的占位符 例如:cursor.execute("insert into people values (%s, %s)", (who, age)) |
| 4 | cursor.executemany(sql, seq_of_parameters) 对在序列SQL中找到的所有参数序列或映射执行SQL命令。 |
| 5 | cursor.callproc(procname[, parameters]) 执行具有给定名称的存储数据库过程。参数的序列必须为过程期望的每个参数包含一个条目。 |
| 6 | cursor.rowcount 只读属性，它返回上次最后一次执行execute*()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()以来所做的任何操作都无法从其他数据库连接中看到。 |
| 8 | connection.rollback() 返回回滚自上次调用commit()以来对数据库所做的任何更改。 |
| 9 | connection.close() 此方法关闭数据库连接。注意，这不会自动调用 commit ()。如果您只是关闭数据库连接而没有首先调用 commit () ，那么您的更改将丢失！ |
| 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返回 None。 |
| 11 | cursor.fetchmany([size=cursor.arraysize]) 获取查询结果的下一组行，并返回一个列表。当没有更多行可用时，将返回空列表。该方法尝试获取由size参数指示的尽可能多的行。 |
| 12 | cursor.fetchall() 获取查询结果的所有（剩余）行，并返回一个列表。当没有行可用时，将返回空列表。 |
下面的Python代码展示了如何连接到现有数据库。如果数据库不存在，那么将创建它，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
下面的Python程序将用于在先前创建的数据库-
#!/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()当执行上述程序时，它会在test.db中创建COMPANY表，并显示以下消息
Opened database successfully Table created successfully
下面的Python程序演示了如何在上面示例中创建的COMPANY表中创建记录
#!/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("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()当上述程序执行时，将在COMPANY表中创建给定的记录，并显示以下两行
Opened database successfully Records created successfully
下面的Python程序展示了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()当上述程序执行时，会产生如下结果
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
下面的 Python 代码展示了如何使用 UPDATE 语句更新任何记录，然后从 COMPANY 表-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()当上述程序执行时，会产生如下结果
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
下面的Python代码展示了如何使用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("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()当上述程序执行时，会产生如下结果
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