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的编写目标是非常小巧,快速,稳定如磐石。您不需要单独安装此模块,因为默认情况下该模块是与Python 2.5.x及更高版本一起提供的。
如果您的计算机上尚未安装它,则可以使用yum命令如下安装它-
$yum install python-psycopg2
要使用psycopg2模块,必须首先创建一个代表数据库的Connection对象,然后可以选择创建游标对象,该对象将帮助您执行所有SQL语句。
以下是重要的psycopg2模块例程,如果您正在寻找更复杂的应用程序,则可以查看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") 该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() 创建一个 cursor ,它将在整个使用Python的数据库编程中使用。 |
3 | cursor.execute(sql [,optional parameters]) 执行一条SQL语句。可以对SQL语句进行参数化(即,使用占位符代替SQL文字)。 psycopg2模块使用%s符号支持占位符 如:cursor.execute("插入人值(%s,%s)",(谁,年龄)) |
4 | cursor.executemany(sql,seq_of_parameters) 此示例程针对序列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。参数序列必须为该过程期望的每个参数包含一个条目。 |
6 | cursor.rowcount 此只读属性,返回最后一个execute *()修改,插入或删除的数据库行的总数。 |
7 | connection.commit() 此方法提交当前事务。如果不调用此方法,则从其他数据库连接中看不到自上次调用commit()以来所做的任何操作。 |
8 | connection.rollback() 自上次调用commit()以来,此方法将回滚对数据库的所有更改。 |
9 | connection.close() 此方法关闭数据库连接。请注意,这不会自动调用commit()。如果只关闭数据库连接而没有先调用commit(),则更改将丢失! |
10 | cursor.fetchone() 此方法获取查询输出集的下一行,返回单个序列,如果没有更多数据可用,则返回None。 |
11 | cursor.fetchmany([size=cursor.arraysize]) 该Example程获取查询输出的下一组行,并返回一个列表。当没有更多行可用时,将返回一个空列表。该方法尝试获取由size参数指示的尽可能多的行。 |
12 | cursor.fetchall() 该Example程获取查询输出的所有(剩余)行,并返回一个列表。如果没有可用的行,则返回一个空列表。 |
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,则将创建该数据库,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,则将显示以下消息-
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()
执行上述给定程序后,它将在 test.db 中创建COMPANY表,并显示以下消息-
Opened database successfully Table created successfully
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-
#!/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, 'Learnfk', 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()
执行上述给定程序时,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程序说明了如何从上示例中创建的COMPANY表中获取并显示记录-
#!/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()
执行上面给定的程序时,将产生以下输出-
链接:https://www.learnfk.comhttps://www.learnfk.com/postgresql/postgresql-python.html
来源:LearnFk无涯教程网
Opened database successfully ID= 1 NAME= Paul ADDRESS= California SALARY= 20000.0 ID= 2 NAME= Learnfk 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代码显示了无涯教程如何使用UPDATE语句更新任何记录,然后从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()
执行上面给定的程序时,将产生以下输出-
链接:https://www.learnfk.comhttps://www.learnfk.com/postgresql/postgresql-python.html
来源:LearnFk无涯教程网
Opened database successfully Total number of rows updated : 1 ID= 1 NAME= Paul ADDRESS= California SALARY= 25000.0 ID= 2 NAME= Learnfk 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代码显示了无涯教程如何使用DELETE语句删除任何记录,然后从COMPANY表中获取并显示其余记录-
#!/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()
执行上面给定的程序时,将产生以下输出-
链接:https://www.learnfk.comhttps://www.learnfk.com/postgresql/postgresql-python.html
来源:LearnFk无涯教程网
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
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