本文实例讲述了Python 操作 PostgreSQL 数据库。分享给大家供大家参考,具体如下:
我使用的是 Python 3.7.0
PostgreSQL可以使用psycopg2模块与Python集成。
sycopg2是用于Python编程语言的PostgreSQL数据库适配器。
psycopg2是非常小,快速,稳定的。 您不需要单独安装此模块,因为默认情况下它会随着Python 2.5.x版本一起发布。
1 2 | pip3 install python - psycopg2 pip3 install psycopg2 - binary |
连接到数据库
以下Python代码显示了如何连接到现有的数据库。 如果数据库不存在,那么它将自动创建,最后将返回一个数据库对象。
1 2 3 4 5 6 7 | #!/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" ) |
在这里指定使用testdb作为数据库名称,如果数据库已成功打开连接,则会提供以下消息:
Open database successfully
创建表
以下Python程序将用于在先前创建的数据库(testdb)中创建一个表:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | #!/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,它将在数据库testdb中创建COMPANY表,并显示以下消息:
Opened database successfully
Table created successfully
插入操作
以下Python程序显示了如何在上述示例中创建的COMPANY表中创建记录:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | #!/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() |
当执行上述程序时,它将在COMPANY表中创建/插入给定的记录,并显示以下两行:
Opened database successfully
Records created successfully
SELECT操作
以下 Python 程序显示了如何从上述示例中创建的 COMPANY 表中获取和显示记录:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | #!/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() |
执行上述程序时,会产生以下结果:
Opened database successfully
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 20000.0ID = 2
NAME = Allen
ADDRESS = Texas
SALARY = 15000.0ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0Operation done successfully
更新操作
以下 Python 代码显示了如何使用UPDATE语句来更新任何记录,然后从COMPANY表中获取并显示更新的记录:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | #!/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() |
Python
执行上述程序时,会产生以下结果:
Opened database successfully
Total number of rows updated : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 25000.0ID = 2
NAME = Allen
ADDRESS = Texas
SALARY = 15000.0ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0Operation done successfully
删除操作
以下 Python 代码显示了如何使用 DELETE 语句来删除记录,然后从 COMPANY 表中获取并显示剩余的记录:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | #!/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() |
执行上述程序时,会产生以下结果:
Opened database successfully
Total number of rows deleted : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 20000.0ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0Operation done successfully
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希望本文所述对大家Python程序设计有所帮助。
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